Heiji Hattori and Kazuha Toyama
 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 Mouris 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.
 Heiji and Kazuha moments
- 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.
- 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.
- Exhausted from chasing Heiji at the tournament, Kazuha falls asleep onto Heiji's shoulder at dinner.
- 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.
- 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.
- Kazuha called her father to help investigate because he knows aditional information about the case; she initially tries to get Heiji to leave with her, but twhn 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 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.
- While holding Heiji and Kazuha hostage, the villain of the case threatens to kill Heiji's "girlfriend" if he doesn't cooperate. When she is about to kill them both, Heiji asks to say some "important last words" to Kazuha, though his delays as he tries to find the right words turns out to have primarily been a ploy to get the gun. Heiji promises to tell Kazuha what he wanted to say if they both survive.
- After the case is over, Kazuha shyly holds Heiji to his promise. He blushes and hesitates, but then tells her that her ponytail had been tickling him, which makes her understandably angry and ruins the serious mood.
- Kazuha comments that Heiji and Conan get along so well, to which Ran asks if Kazuha is jealous. Kazuha protests that she isn't.
- Heiji glances over his shoulder as the girls leave, watching Kazuha, until Conan reassures Heiji that Kazuha won't be in danger from the serial arsonist.
- During a deduction competition where the winner gets to choose between a baseball game and a play, after seeing Kazuha's tears of frustration, Heiji decides to lose on purpose so that Kazuha can win and see what she wants. However, while trying to lead Kazuha to the answer, he gets caught up in the excitement of deduction and solves the case by accident. Kazuha is outwardly disappointed, but refuses when Heiji offers to go to the theater instead, to his confusion. In her own thoughts she realizes that what she'd wanted to see most was Heiji's expression when he's solving a case.
- 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 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 bring 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 not lose.
- 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 finally gathers her courage and tells her feelings to Heiji, but Heiji didn't hear because he ran off to tease Shinichi about confessing his feelings to Ran just as Kazuha was about to confess.
 Movies and OVAs
In the seventh movie, Heiji realizes that Kazuha was his first love and he smiles fondly at the realization.
In OVA 9, 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.
- Fans of the Heiji-Kazuha pairing sometimes refer to them as "KazuHei" or "HeiZuha."
- In most openings, they have appeared together.
 See also
- ^ Manga Volume 19: Files 185 (Stabbed Wallet Case)