Heiji Hattori and Kazuha Toyama serve as the beta couple for Detective Conan and a foil for Shinichi Kudo and Ran Mouri's relationship.
 Relationship analysis
Heiji and Kazuha grew up together and are easily each other's best friend. Neither of them have been shown to have other close friendships, though Heiji does have a rivalry with fellow kendo practitioner Okita. They often spend time together, and Kazuha typically comes along when Heiji visits the Mouri's or vice versa, getting caught up with Heiji in the criminal investigation. Kazuha and Heiji both wear good-luck charms that Kazuha made with pieces of the handcuff chain that stuck them together temporarily as children. Kazuha and Heiji have both shown jealousy when the other appears interested in someone else, but they are not officially in a romantic relationship. Kazuha has demonstrated awareness of her affection for Heiji, but has been either too shy or otherwise interrupted any time she tries to tell him. Heiji, in contrast, is either emotionally oblivious or purposefully ignoring his feelings for Kazuha for most of the series. Heiji has yet to attempt any sort of confession to Kazuha, but he is very protective of her. In one of the most recent cases, Heiji thought that Kazuha was being taken away by a couple of strange men. Furious, Heiji pins the guy holding Kazuha and yells at him saying "Whatcha doin' to my Kazuha?!". Seemingly confessing that she's his girlfriend out loud. But because he's too embarrassed to admit his own confession, he says that she has no proof to say that he actually confessed to her.
 Heiji and Kazuha moments
Kazuha accuses Ran of being the Kudo that Heiji is in love with.
- Kazuha watches Ran so intently that Ran can sense it, then appears and threatens Ran that if she has any designs on Heiji, she'll have to compete with Kazuha and their childhood bond. After Ran watches Heiji and Kazuha interact, and Heiji explain that the "Kudo" he has been talking about is actually a guy, Ran asks if they are a couple. They both deny it, citing their fathers' connection, but Kazuha admits with a blush that she had been following Heiji and the Mouris for some time to make sure Heiji didn't "get carried away by some Tokyo girl."
- When Heiji leaves to investigate the murder, Kazuha calls after him to be sure he has his lucky charm for protection. Heiji confirms that he does and tells her to not worry.
- Kazuha reveals with a blush that she hid a piece of the handcuffs in the charm she gave to Heiji, though he may be unaware of it.
- When Heiji is shot in the stomach and appears to be dying, Kazuha cries and embraces him (though this makes Heiji angry, because he merely wanted to sleep from being tired, not fatal blood loss).
- Kazuha accompanies Heiji to Tokyo to attend a wedding on behalf of his mother, and blushes when she claims coming along was only a favor to Heiji's mother.
- Kazuha treats Ran coldly, to Ran's confusion, until Kazuha reveals she is annoyed that Ran and Heiji are wearing matching shirts like they did before in Osaka, as if they had planned it as a couple.
- At a temple for prayers, Heiji says Kazuha should ask for nice legs, causing Kazuha to blush.
- After the case concludes, Ran pushes Kazuha to wear the same sort of shirt as Heiji. When Heiji notices, Kazuha blushes and says she'll change. Heiji says he doesn't mind... because it makes them look like siblings. Kazuha looks nonplussed by the unromantic comparison.
- When Heiji suggests that he and Kazuha might have to cuddle with each other so they won't get a cold while camping outdoors, Kazuha blushes and imagines a sleeping Heiji putting his arm around Kazuha inside the tent.
- Heiji frantically calls Kazuha's name and immediately calms down when he sees her. When Yuzo Takeda states how after both Conan and Heiji learned that the place the girls were going was cursed and dashed out, Kazuha, blushes and smiles,then asks if he was worried. Blushing, Heiji denies that's not the case.
- Heiji gets a horrified expression when he sees Kazuha tangled in wires; he proceeds to repeatedly shout her name, asking her to wake up. And when Kazuha does wake up, Heiji has a content look on his face.
- When confronting the Liuji family on Kazuha being attacked by the murderer, Heiji mockingly states that after Kazuha wakes up, she'll reveal who attempted to kill her. The classic "red, angry" mark can be seen on his head, meaning how furious Heiji is of who tried to hurt Kazuha.
- Kazuha blushes and twitches her eyes when Heiji tells her to "take off her clothes" (it had to do with the case). He even tries to take off her shirt, himself. Earning him a well deserved slap in the face.
- Heiji looks at the charm Kazuha secretly slipped into his things, wondering if it's what protected him. Ran realizes where he got it, causing him to blush and say he should have thrown it away already, although instead he tucks it safely away to keep.
- Kazuha says she has thought about staying forever young and beautiful. When Ran asks if she wants to because of liking Heiji, Kazuha blushes and tells Ran to not talk so loud.
- After the murder occurs, Kazuha happily tells Ran that the criminal will be found soon because Heiji flipped his cap from back to front, signifying his becoming serious. She adds with a blush that Ran shouldn't praise him, because Heiji's weakness is that he's too confident, causing Ran to hug Kazuha and call her cute.
- After the second murder, Heiji tells Kazuha not to wander off, causing her to blush. She takes him at his word and follows as he investigates, as well as offering to protect him with her blessed arrow. Heiji doesn't think much of it, but Kazuha privately affirms that she means it seriously.
- In pursuit of a memorial stone, Heiji runs nearly off a cliff, saved only by Kazuha swinging him around to trade places. As a result, she falls, and Heiji dives after her, catching onto a tree in the cliff face with one hand and her with the other. Kazuha believes the branch Heiji is holding will break if he tries to pull her up, and stabs the hand holding her wrist with the mermaid arrow to transfer her "long life" to Heiji. To her surprise, Heiji still doesn't let go and gets them both to safety despite the injury.
|| Even if I die, I won't let you go.
— Heiji refusing to drop Kazuha.
- After Kazuha expresses her relief that Heiji's hand has apparently already healed overnight, Heiji thinks to himself that he won't let her be hurt (even, apparently, with only feelings of guilt). He showed her and Ran the wrong hand, hiding the bandaged one in his pocket.
|| Fool. You're too naive. I will never... never... let you be hurt.
— Heiji's secret promise to Kazuha.
- Kazuha overhears Heiji talking secretively on the phone with Shinichi, and assumes that he is "having an affair" with a mysterious woman. She attends the party with Heiji, suspicious that the "woman" asked Heiji to come.
- When the murder occurs, Heiji tells Kazuha to keep the suspects staying put, trusting that she'll do so.
- Kazuha tells Ran not to worry about Conan helping Heiji investigate, and proudly adds that since Heiji's on the case, no one will get hurt.
- At the kendo tournament, Kazuha blushes as she tells Shizuka that Heiji has gotten very strong as a kendo fighter. She also helps Heiji put his gear on.
- Kazuha reassures Heiji's kendo team after Heiji is to preoccupied with the murder investigation to play on the team, saying that they'll win and when they do they'll rub it in his face.
- Kazuha grabs Heiji's hand to get to the final match in time.
- Exhausted from chasing Heiji at the tournament, Kazuha falls asleep on Heiji's shoulder at dinner. Causing Heiji to blush slightly.
- While in the car, Kazuha overhears her father telling Heiji's father that since Kazuha is reaching marriageable age, he'd rather she marry Heiji than some "irresponsible punk". Kazuha blushes at the thought, and is disappointed when her father tells Heizo it was a joke.
- Heiji berates Kazuha for giving Kogoro, Ran, and Conan the exact same information and tour he did when they first came to Osaka, making Kazuha angry and embarrassed at Heiji's statement.
- Heiji leads Kazuha away from the role play group by the arm when she tries to interact with them more, calling them "Weirdos"
- When Kazuha loses her wallet, she refuses to give up looking for it because it had her good-luck charm (with the handcuff chain) and other charms to ward off a murder case inside.
- Heiji tells Kazuha not to cry in an uncomfortable voice after a raindrop falls on her face, making her look like she started to cry over her wallet.
- Kazuha called her father to help investigate because he knows additional information about the case; she initially tries to get Heiji to leave with her, but then leaves with just Ran because she wants to see his triumphant expression when he's solved the case. When he gets that expression, she blushes happily and assures the others that Heiji knows who the criminal is already.
- Heiji looks the most concerned when he hears Kazuha's scream in the distance.
- Heiji pays close attention to Kazuha as she explains what happened when she & Ran were walking on the bridge to pick up Conan from the crime scene.
- Kazuha expresses a hinge of jealousy, as well as annoyance, of Heiji guessing what kind of bathing suits the girls on the beach are wearing.
- Kazuha gives a mild, red blush when Conan announces that Heiji knew what kind of swimsuit she would be wearing.
- Heiji interrupts two men flirting with Kazuha and Ran. When asked who he is, Heiji answers "My...", which causes Kazuha to blush, before he adds she's merely his childhood friend and a bit annoying, to Kazuha's disappointment. Ran comments in the background that his statement is phrased oddly, as if that might not be what he originally intended to say.
- Heiji and Kazuha are held hostage in the attic of Misari Ito's House
- Heiji tries to get their hands free from the handcuffs, but winds up hurting Kazuha when he messes up. Making her call him an idiot while Heiji tells her to be quiet or the others will hear them.
- When Heiji drops the pin he was using to unlock the handcuffs, Kazuha becomes panicked and Heiji asks if she has some type of wire with her. She tells him that was the only thing she had.
- Kazuha asks Heiji if it would just be better for them to solve the code they gave them, since they said they would be released unharmed if they did.
- Heiji and Kazuha are threatened by the two kidnappers that if they didn't solve the code, then they would be as cold as the other guy they caught.
- Kazuha whispers Heiji's name softly in fear and Heiji comforts her by saying that they don't know "That Guy" (referencing Shinichi), causing Kazuha to become confused at his statement.
- Kazuha looks at Heiji with concern and worry as he is abused by the two kidnappers.
- Kazuha asks Heiji if he is alright and that he has to hang on.
- When Heiji is punched in the stomach by one of the kidnappers, Kazuha says his name with deep concern.
- After Heiji gets his hair pulled by one of the kidnappers to get his ear sliced off, Kazuha exclaims Heiji's name in fear for his safety.
- Kazuha yells at the Kidnapper with the knife to stop with tears in her eyes. Not wanting any harm to come to Heiji.
- Heiji leads Kazuha to the window where he exclaims in surprise that Shinichi (Conan) was leaving them. Kazuha tells him that he's probably thinking of a way to save them but Heiji doubts her claims.
- Heiji, frustrated at their situation, says that he has no other choice but to break the window. Causing Kazuha to freak out at his proclamation.
- Heiji turned around when Kazuha began to recount how her father knew Kusukawa-San was a gambler and scolded her for not telling him sooner.
- When Kazuha asks Heiji if he has the entire answer to the problem, Heiji smiles and says that he does saying that it is easy to remember if you gamble.
- Misari threatens Heiji that if he messed up on the top part of the problem than he would find himself covered in his Girlfriend's (Kazuha's) blood.
- Heiji and Kazuha are both horrified when they realize Misari's full plan.
- Misari asks Heiji if he has any last words to say before she kills him, After a while and a threat, Heiji says that his last words were directed to Kazuha right behind him.
- Kazuha's eyes widen when he says that his final words are for her.
- When Misari says that his Girlfriend (Kazuha) won't last much longer than him, he says that it's something that he's been wanting to tell her forever and asks for the gun to be put down until he is finished.
- When Misari starts to rush Heiji on his last words to Kazuha, he says that he wants to make sure that it is perfect so that she remembers it when she's up in Heaven. Causing Kazuha to blush at his statement.
- When Heiji's plan is foiled to get the gun away from Misari, he gets kicked down and Kazuha cries out his name in concern and fear.
- While Misari is counting down before she shoots Heiji, He tells Kazuha that he was telling the truth when he said that his final words were for her. Saying that he almost said it over and over and that every time he felt her tremble against his back he- and he stops right there before he embraces for the impact of the gun shot.
- Kazuha listens to this in a horrified gaze with tears filling up her eyes.
- After Heiji is released and is about to leave with Misari, Kazuha looks at him with scared eyes and asks if they survived this than he would tell her what he was about to say. Causing Heiji to smile and reply that he'll keep saying it until she gets tired of it.
- After Misari is arrested along with her accomplices, Heiji tells Shinichi (Conan) that the case was close in many ways. Thinking back to the point where he was almost shot in front of Kazuha when he was telling her his final words.
- Heiji started to blush hard when Kazuha asked him what his final words were and scratched his cheek as he started to say them over to her again, but he gets embarrassed and scared and told her that her pigtail was bothering him every single time she moved. Angering Kazuha and causing Shinichi to wince with sympathy, who was listening on the other side blushing as well for his situation.
- Heiji and Kazuha recall their hostage situation when they spend the night at Ran's apartment.
- Before Kazuha could say anymore about Kogoro solving the deciphered code (Which was actually Shinichi's doing), Heiji cuts her off and says that it didn't matter anymore.
- When Kazuha looks at Heiji confused about the Arsonist, Heiji takes the time to explain to her and the others what the arsonist is trying to accomplish.
- Kazuha wishes Heiji and the others luck on their detective business when she heads off with Ran. Heiji smiles at her and replies back "OK."
- When Kazuha comments that Heiji and Conan get along really well, Ran asks if she's jealous of Conan. Making Kazuha deny any such thing.
- When Heiji and the others were late coming back to Ran's apartment, Kazuha questions Heiji furiously over the phone.
- Heiji explains that they are at a client's house and Kazuha is furious with the news, saying that they would be back by now.
- Heiji agrees and says that they were on their way when a couple of firetrucks came by and made them worried. So they went back to discover the house was in flames. Causing Kazuha to become surprised with the news.
- Kazuha calls Heiji an Idiot since she thought she had found the perfect shirt that would fit him when she and Ran went out shopping together. Wanting to show him the shirt when they got home.
- Ran reassures Kazuha saying that Heiji and the others would be back home soon.
- Kazuha becomes severely frustrated with Heiji when it becomes late at night, saying to forget them and go to bed since they're going to Tropical Land in the morning. But Ran stops her before she went to bed by asking to put the teruterubozu over her Dad's window.
- When Heiji hears that Kazuha and Ran received a Red Horse key chain, he yells at Kogoro to tell him what block his apartment is on. With concern in his eyes for their safety.
- After Kazuha and Heiji see each other again at Ran's place, he asked her in a concerned voice what had happened.
- Kazuha is frustrated and angry when Heiji cancels their plans to go to Tropical Land.
- When Kazuha and Ran are freaked out about the burnt down building, Heiji asks them why they even bothered to come along with them in the first place with an irritated tone of voice.
- Kazuha replies back to him that they came because they wanted to finish the case as quickly as possible so that they could resume their plans to go to Tropical Land together.
- It is revealed that Kazuha talks to Heiji's mother frequently and they talk for quite some time together.
- Heiji and Shinichi (Conan) are frightened when they are caught talking about Kazuha and Ran's calling habits.
- With some common knowledge given by Kazuha and Ran's conversations, Heiji and Shinichi (Conan) are able to figure out the rest of the case.
- Heiji and Kazuha were both at the Mouri's apartment to greet Conan when he returned home.
- When they arrive at the restaurant, Heiji and Kazuha sit right next to each other.
- Heiji and Kazuha are both equally surprised when they hear different plans from each other to go to see Koshien and Takarazuka, causing them to break out into an argument.
- When Kazuha says that they can't do both after Heiji mentions the High School Baseball finals, Heiji leans in closer to her and asks if she got the tickets from one of the five women who absolutely love Takarazuka.
- Heiji smiles at Kazuha and offers the unsolved murder case as a competition to see if they go to Koshien or Takarazuka.
- Kazuha is angered at the proposal, seeing as how Heiji is a better detective than she is and that she'll never win in a competition revolving around deduction and reasoning against him.
- Heiji says to Kazuha that it is sneaky of her to get 2 people to help her out with a annoyed look on his face, Kazuha just sticks her tongue out at him.
- Kazuha stands right behind Heiji as he is looking over the spot the dead body was found.
- Heiji explains out loud that they don't know if the murderer was an outsider to begin with and stands up to be right besides Kazuha with a smile on his face.
- While Megure lays out the pictures in front of them, Heiji stands close to Kazuha's shoulder.
- As Heiji is explaining his reasoning behind the ink on the blocks, he smiles and looks back at Kazuha as he continues on with his explanation.
- Kazuha stops herself before she praises Heiji's reasoning, reminding her that she is in a competition with him and that she can't allow him to win and figure out the dying message before her.
- When Heiji finally figures out what the dying message means, he smiles and looks back at Kazuha. Apologizing that he has solved the message and that he's going to win the competition.
- Heiji then realizes that Kazuha is frustrated and that she is starting to cry over the fact that she can't figure out the dying message. Making him soften his expression on his face to concern for her feelings.
- Heiji thinks Kazuha's name in a gentle tone of voice and continues to look at her in a gentle fashion.
- After remembering what Shinichi said to him about competitions about deductions, he decides to let Kazuha win and he starts to drop hints to her on how to win the competition.
- As Heiji drops hints to Kazuha about solving the dying message, he keep turning his direction to gaze into her eyes to see if she gets what he is trying to do. Making Shinichi (Conan) realize what he is doing and smile at his reasoning behind playing dumb all of a sudden.
- When Megure says that Kazuha's reasoning must be wrong, Heiji stands up for her and says that her deduction wasn't wrong at all.
- When Heiji starts to get wrapped up in solving the case after he has put all the pieces together in his head, Shinichi (Conan) starts to warn him silently that their main intention was to let Kazuha win the competition.
- Shinichi (Conan) Is dumbfounded when Heiji solves the case, since Heiji's main intention was to let Kazuha win the competition so that they would all go to Takarazuka instead of Koshien.
- Heiji is frightened when he realizes that he accidentally got too wrapped up in solving the case and turns to hear Kazuha congratulate him and says that she'll practice the Tiger's Fight song and turns to leave him.
- Heiji cries out for Kazuha to wait so that he can tell her that they can go to Takarazuka.
- When Ran suggests that they try to make Heiji want to go to Takarazuka instead, Kazuha denies this and says that the only thing that she wanted to see was Heiji's face after he solves a case and smiles at his expression.
- Heiji sits and pouts at his accidental victory and wonders how he messed up on his plan to allow Kazuha to win, making Shinichi (Conan) call him an idiot.
- Kazuha becomes irritated when Heiji comments on how the female magicians are a couple of "beauties".
- Heiji is outwardly jealous when Kazuha & Ran mention that they hugged Hoshikawa and he angrily asks why she [Kazuha] hugged him.
- Heiji removes Kazuha's arms from Hoshikawa's arm in a jealous manner.
- Heiji is very irritated when Kazuha praises Shinichi as having the best deductive mind.
- While talking about the murder case with Conan, Heiji mentions that whenever he sees Kazuha be flirtatious with or talking about another guy, he gets annoyed and he can't concentrate. He asks Conan why that happens; Conan realizes Heiji's feelings, but merely calls Heiji a child because he's so oblivious to the truth.
- Heiji gets extremely irritated when Kazuha mentions that Hoshikawa calmed her down.
- Heiji tells Kazuha to stay put with Ran while they investigate; Ran recognizes Heiji's jealousy, but Kazuha is oblivious.
- Heiji blushes and freaks out a little when Kazuha tightly hugs his arm to demonstrate why a magician couldn't be the killer.
- At the end of the case, Heiji states he figured out why he doesn't like seeing Kazuha flirt with other guys: after a conversation with Megure he's concluded that he thinks of her as a subordinate, like her father is a police subordinate to his father. This, understandably, frustrated Kazuha and they start to argue.
- In a flashback to a junior high ski trip, Kazuha stays out at the foot of the slopes despite a broken ankle because she wants to watch Heiji skiing. Heiji appears in a deliberate splash of snow to tease her (for the fifth time), and then gets teased by his classmates for being around Kazuha and her female classmates. With a faint blush, Heiji tells Kazuha to go back inside so she doesn't get sick, which causes her to blush in return and agree to do so. After he leaves, Kazuha's classmates tease her gently about liking him.
- At lunch, some boys tease Heiji and Kazuha about being a couple when Kazuha sits next to Heiji rather than the other girls in their class.
- Kazuha tries to stop Heiji from investigating an old murder despite an incoming snowstorm. They overhear Sonoko teasing Ran and Shinichi about being a couple, assume it's directed to them and blush (and Heiji starts to vehemently deny it until he realizes Sonoko isn't looking at them).
- When Heiji berates his mother for following him on the ski trip to add to her videotape collection of him growing up, Kazuha blushes and thinks that she would like to see those tapes.
- Kazuha's classmates realize that Kazuha got herself promoted to the advanced skier group to be in the same group as Heiji, despite not being very good at even getting off the ski lift. She admits it and asks them not to tell Heiji about it. She also accompanies Heiji through the rest of his investigation, which also aggravates her ankle. He call her an ahou, but carries her piggyback and thanks her for her assistance in what he's figured out about the case so far. Heiji also concludes that she got into the advanced skier class to show off, unaware that Kazuha is blushing and smiling from the closeness as he carries her, and to be closer to him was her true aim.
- When Heiji looks intently at Kazuha blowing on a pinwheel, Kazuha blushes, although Heiji was actually staring at the pinwheel as a clue about a murder case.
- As Heiji leaves for the detective competition with Conan, Kazuha calls out to Heiji with a blush that as the representative from Osaka, he can't lose.
- When Hakuba asked if Heiji had told anyone where he was going, Heiji answers he has, while thinking of Kazuha.
- After arriving to the island, Kazuha and Heiji call for each other's name. The former for confirmation and the latter out of happiness.
- When looking at the picture of the murder victim, Kazuha is behind Heiji, with her hand on his arm.
- Heiji tells Kazuha to stay behing while he and Conan go investigate, and when she asks why, he responds by telling her she'll just be a drag. However, Ran explains that Heiji is only doing it because he doesn't want Kazuha in danger.
- Heiji teases Kazuha that she shouldn't sleep with her belly showing.
- After learning about Furinkazan, Kazuha blushes while thinking about Heiji.
- Heiji worriedly asks Kazuha what's wrong, after the she calls him.
- Yui Uehara notes that Kazuha likes Heiji, and counsels her that while waiting can be enough, sometimes it's better to act; if she doesn't, the chance to tell Heiji her feelings might disappear.
- Kazuha decides to confess to Heiji and drags him off somewhere private, despite his protests and attempts to excuse himself. However, in the end, she can't bring herself to do it and walks off with a deep blush to join Ran. Heiji once more acts oblivious to Kazuha's intentions.
- Kazuha is asked by a family acquaintance to make a good-luck charm for his upcoming tennis tournament. While she is caught up in aikido practice the day he is supposed to pick it up, Heiji accidentally gives the man Kazuha's personal charm rather than the one she'd made. Heiji goes to Tokyo to get it back; when he asks Kazuha why she even came along, she blushes and doesn't answer. Later she privately confides to Ran that she came to get the charm back without letting Heiji look inside, because she secretly keeps a small photo of his face inside it. Ran agrees to help, but teases Kazuha with the possibility of showing Heiji the photo.
- After the case is solved, the charm is released from police evidence to Heiji, which causes Kazuha to panic and run after him. By the time she arrives, Heiji has already opened the charm—but the tennis player scribbled all over the picture in frustration at realizing that Kazuha wouldn't return his feelings, so Heiji concludes that Kazuha thinks he's ridiculous rather than being in love with him.
- Kazuha tells Ran that she'll gather up her courage and confess her feelings to Heiji after she hears that Shinichi had confessed his love to Ran in London.
- Heiji is scared and nervous when he feels Kazuha "glaring" at him from behind.
- Kazuha finally gathers her courage and tells her feelings to Heiji:
|| Ya might have already heard this from Kudo-kun, but...In London, apparently Kudo-kun confessed his feelings to Ran-chan.That's why, though I wouldn't have said this...The truth is...The truth is, I also...Since a long time ago...I... I LIKE YA VERY MUCH!
- Kazuha is disappointed when Heiji didn't hear her confession; he ran off to tease Shinichi about confessing his feelings to Ran just as Kazuha was about to confess.
- Kazuha is envious and jealous of Conan's close relationship with Heiji.
- Heiji is shocked when he sees Kazuha at the drug transaction site talking with a mysterious man.
- Heiji is disgusted when Kazuha seemingly flirts with the mystery man.
- When Kazuha falls into the man's arms, he becomes unable to concentrate on the case at hand.
- While Heiji is talking to Conan, he keeps his eyes on Kazuha's interactions with the mystery man.
- Heiji's eyes widen when Kazuha falls into the mystery man's arms.
- Heiji slams the man by the neck and angrily exclaims:
|| Whatcha doin' to my Kazuha!?
- Heiji is freaked out when Kazuha comes up right besides him out of nowhere during his introduction to the movie. Calling him an idiot and they get into a small argument.
- Kazuha wishes Heiji good luck when he goes off to investigate.
- Kazuha doesn't enjoy her time with Ran & Sonoko when they sight see together through Kyoto since she is thinking about Heiji.
- Kazuha is openly jealous and sadden with how Heiji looks for his first love in Kyoto whenever they visit. Expressing this to Ran and Sonoko in a sadden tone of voice.
- Heiji explains to Conan that he met his first love in Kyoto and it shows a young girl resembling Kazuha as she played with a ball and singed.
- Kazuha is afraid and hurt that Heiji has supposedly met his first love
- Heiji waves at Kazuha from the upper level of the house with a smile, but Kazuha pouts and says that he really makes her angry.
- When Kazuha asks who the criminal could be, Heiji looks at her and replies that Ryuen-San, Saijou-San, Mizuo-San, or Chika Suzu-San could be the killer.
- Heiji looks wearily at Kazuha when he almost slips Shinichi's name out loud in front of her and the others.
- Kazuha rides with Heiji on his Motorcycle and chases the same man who had almost murdered him in the woods. Holding onto him tightly as they jumped a wooden ramp.
- Heiji tells Kazuha to stay with his Motorcycle as he goes off to chase the criminal but Kazuha calls out his name to stay with her.
- Right before the criminal is about to finish off Heiji, Kazuha arrives just in time and hits the criminal on the head. While motioning the non-existent detective where the criminal is.
- Kazuha asks if Heiji is alright, to which he asks where the detective is. Kazuha reveals that there wasn't any detective to begin with.
- Heiji asks where Kazuha learned how to ball up her sock and make a weapon, saying to her that she can be a terrible woman with a smile on his face. Passing out in her arms.
- Kazuha freaks out about Heiji's condition when he passes out.
- When Heiji wakes up in the hospital the next morning, Kazuha is at his bedside. Heiji says her name softly and Kazuha gives him a gentle smile of relief.
- Kazuha asks Ran to look after Heiji while she goes out.
- Heiji is worried when he learns that Kazuha has been kidnapped by the criminal through a phone call on his cellphone from her.
- Kazuha tries to warn Heiji through the phone before the criminal hangs up that they'll kill him and that he shouldn't come.
- Heiji is worried and concerned for Kazuha's well being and says her name twice in concern and finally gives up realizing that the connection has been lost.
- Before one of the other men in the temple could hurt Kazuha with their swords, Heiji quickly defends her by counter attacking him and pushing her behind him.
- Before Heiji and Kazuha leave the temple grounds, they are stopped by the rest of the men of the group and Heiji wraps his arm around Kazuha's shoulder protectively.
- Kazuha yells for Benkei to stop fighting because the Heiji there was an impostor which turns out to be Shinichi the entire time.
- Heiji reveals himself as being one of Benkei's men in disguise and apologizes to Kazuha for making her wait. Making her angry and yelling at him and calling him an idiot.
- Heiji turns her around to cut away her ropes and protects her as the other henchmen try to attack her and Shinichi.
- Heiji makes Kazuha swear that she won't tell anyone that she saw Shinichi that night.
- Heiji runs away with Kazuha by the hand and leads her away from Benkei's men, only to be chase into pursuit.
- Kazuha tells Heiji that Benkei's sword is one of the many drawers of the room she was held captive in.
- Heiji is frustrated with trying to figure out the rest of the Temari song when Kazuha starts to sing it and reveals the location of the sword through the lyrics.
- Heiji looks at her surprised when she started to sing the Temari song, possibly remembering his first love.
- Heiji moves in front of Kazuha protectively as he grabs her hand with his other hand on the found sword. Threatening Benkei to stay away from them through his body language.
- Heiji protects Kazuha as he deflects the other swords as they run through the halls and out of the temple room.
- Heiji tells Kazuha that he's going to distract the others while she runs and escapes. When Kazuha refuses, Heiji tells her again to run and leave with a serious look on his face. Causing Kazuha to say his name gently and finally agreeing to leave when she is told to escape.
- After Benkei and his gang were gathered up and arrested, Kazuha runs up to Heiji in relief and Heiji smiles at her as they reunite.
- Heiji corrects her on the mistake she made while she sang the Temari song again at the train station. Then he asks her where she learned the song in the fist place.
- Kazuha tells Heiji about the time when they were children and how she had brought him along to go visit her relatives, dressing up in a Kimono and looking for him since he had left before she was finished with her preparations. When she didn't find him at the Castle grounds, she found a ball and began to play with it while singing the song her relatives taught her. With the Cherry Blossoms flying in the air, the whole scene turns out to be what Heiji saw when he woke up after being knocked out.
- Heiji realizes that Kazuha was his first love and he smiles fondly at the realization.
- Kazuha asks if Heiji had finally met his first love in Kyoto and if it was the dancer woman and Heiji tells her that he'll never tell her. Teasing that it'll be 1,500 years before he tells her.
- When Heiji meets Conan during a hunt for clues for the case, he reveals that he has a wristwatch bomb as well and that Kazuha is being held as a hostage inside the amusement park against him.
- Heiji says that Kazuha doesn't even know that she's being used as a hostage and that she is probably enjoying herself in the amusement park. Smiling at the thought of her enjoyment and naivety to the situation she's in.
- Kazuha becomes frustrated when she keeps getting Heiji's voice mail whenever she tries to call him while she waits for him inside Miracleland.
- Kazuha reveals that Heiji was the one who invited her to Miracleland with him, but told her that he had to take care of something for work first.
- After the case is solved, Heiji is seen standing right next to Kazuha and smiling.
- Heiji and Kazuha ride the Super Snake Roller coaster together and Kazuha teases that Heiji didn't bring his extra pair of pants. Angering Heiji and making him ask why he would need them.
- Kazuha teases that if Heiji was scared then he didn't have to raise his hands, making Heiji proclaim that he isn't scared but he wasn't going to put his hands up either.
- Kazuha, not realizing that Heiji is freaking out about the leftover wristwatch bomb on Genta's hand, laughs that Heiji is overreacting a bit much.
- Kazuha runs up to Heiji and asks who he is talking to, surprising him and making him lose his balance. Causing him to fall and making Kazuha believe that he fell completely out of the building.
- Heiji tells Kazuha that she scared him and that she almost killed him, making Kazuha apologize for frightening him.
- Kazuha teases that Heiji must be talking to someone important and Heiji calls her an idiot and tells her that he's talking to Shinichi.
- Heiji apologizes to Shinichi and tells him that Kazuha is poking her nose into other people's business again while smiling at her.
- When Kazuha interrupts Heiji's conversation with Shinichi again, he stops everything and listens to her speak with an annoyed look on his face.
- Heiji tells her to go by herself if she wanted to go to the Chinese Valentine Celebration while shooing her away with his hand to give him some space.
- Kazuha starts to plea with Heiji to go with her to the Celebration even if they left on the same day and didn't stay at a hotel to spend the night.
- Heiji replies with an annoyed face that he wouldn't stay at a hotel even if she suggested it because of a fire that happened last year.
- Kazuha calls Heiji stingy with a pouting look on her face.
- Kazuha asks where Heiji is going and he tells her to tell the teacher that he left to find Weaving Maid at the Vega Hotel. Causing Kazuha to become confused at his statement.
- Heiji and Kazuha are together having a fun time together.
- When asked by Satoshi Kawaguchi if the two were a couple, both teens blushed and vehemently denied being one.
- Kazuha tells Heiji to be careful when he goes to help with the hijacked blimp, and he promises he will.
- Heiji saves Kazuha from almost getting shot by a bullet; when the danger is over, Kazuha begins to tear up because Heiji got hurt because of her, with Heiji asking her not to. It fails, and Kazuha cries and hugs Heiji; he tells her it hurts, despite smiling.
- When talking to Conan about the case, Kazuha is holding up Heiji's phone, since the detective is having his injury tended; Kazuha is still upset, but Heiji affectionately pats her head, telling her it's alright. Then, Kazuha begins crying again and tackles Heiji
Heiji and Kazuha's reaction when a reporter inquired when they will be married
- Heiji tells Kazuha to bring her ear closer so he can whisper something to her. She blushes and does so, ending in him calling her an idiot.
- Ran teases Kazuha about thinking about her and Heiji having a wedding.
- In the credit scene, Heiji and Kazuha are seen doing karaoke together.
- Heiji is being interviewed on TV when Kazuha suddenly appears. They argue briefly, and the reporter asks them when they'll get married, shocking them both briefly into silence.
- Heiji smiles fondly at Kazuha taking care of the baby boy. Kazuha explains she had some skills with children before and abruptly tells Heiji, while blushing, "I want a baby." This causes a deep blush to appear on Heiji's face and quickly call her an idiot.
- Heiji and Kazuha are seen eating Okonomiyaki together and having a fun time.
 Opening Themes
- Both Heiji and Kazuha appear in the opening.
- During the final scenes of the opening, Heiji and Kazuha are seen smiling together for a picture.
- Heiji and Kazuha are riding on the former's motorcycle.
- At the opening's end, they can be seen close together, with Kazuha's hand on Heiji's shoulder.
- Heiji and Kazuha are seen together, presumably talking, until they both look up into the sky.
 Ending Themes
- Kazuha is standing behind a crouching Heiji, with her hands on his shoulders.
- A child Heiji and Kazuha are seen briefly, both running in the opposite direction of a young Shinichi and Ran.
- Heiji is teasing Kazuha by holding a baby snake, and Kazuha is trying to get away from him.
 Drama Episodes
- Kazuha smiles warmly while watching Heiji do his role.
- After the accident on the shoot, Kazuha stays at Heiji's bedside, and calls out his name with worry in her voice. She then grabs his hand, with the omamori locket in her hand.
- Kazuha notices Ran watching Heiji very closely.
- A jealous Kazuha confronts Ran forcing Ran to explain herself. Thankfully, Ran explains she was watching Heiji because he reminded her so much of the guy [Shinichi] she thinks about.
- Kazuha explains the story to Ran about how she and Heiji were accidentally handcuffed to one another when they were little and shows Ran the piece of the chain she keeps as a lucky charm. Ran asks if she and Heiji are dating but Kazuha, embarrassed, remarks that she thinks of herself as more of an older sister to Heiji.
- Sato teasingly warns Shinichi and Heiji to be careful with their bonds towards Ran and Kazuha, respectively.
- Fans of the Heiji-Kazuha pairing sometimes refer to them as "KazuHei" or "HeiZuha."
- In most openings and endings, they have appeared together.
- Heiji & Kazuha have gone to the same school since they were in pre-school.
- Heiji & Kazuha are referred to as the Shinichi and Ran of Osaka.
- Both of their birthdays have yet to be revealed in the Conan Universe.
- They are the 2nd couple to be introduced as childhood friends who became something more.
- Their parents have known each other before they were even born. Making their families close.
- Everyone at their Jr. High School & High School have commented that they're a couple.
- Much like Shinichi with Ran, Heiji is deadly afraid of Kazuha's anger.
- Heiji and Shinichi often talk about their relationships with their "girlfriends" much like Kazuha and Ran do about their "boyfriends".
- Heiji and Kazuha are equally jealous of each other when another person has an attraction to them.
- Heiji and Kazuha's relationship is similar to Kogoro and Eri's, as both pairs are childhood friends, who fall in love with each other, and fight/insult each other a lot to hide their true feelings towards each other
 See also
- ^ Manga Volume 19: Files 185 (Stabbed Wallet Case)