|Japanese name:|| 大岡 紅葉 |
|First appearance:|| Manga: File 962 |
Anime: Movie 21
|Appearances:|| Chapters: 9|
|Japanese voice:||Satsuki Yukino|
Momiji Ooka is a second-year student from Kyoto Senshin High School and a champion of Hyakunin Isshu karuta. Her family is likely wealthy since she has a butler. Momiji claims Heiji Hattori 'proposed her when they were little' and thus believes that they will be romantically involved in the future.
She was once part of an elite karuta association called Nagoro-kai. She was the greatest student of the group's founder, Nagoro Shikao. However, after the group was disbanded she joined another association called the Satsuki-kai.
Momiji appears to be an extremely competent detective, as she saw through a trick merely based on a sound she heard in a phone call with her butler, Muga Iori, before Conan, Heiji or Bourbon did. Later, Muga says that her deduction was great as usual, implying that she regularly solves cases and also says that Heiji's great deductive skill was to be expected from the person that Momiji chose as her partner.
Momiji is involved in the plot of movie 21 which will center around Heiji and Kazuha's romance. She is shown crying in the movie artwork. The trailer of the movie shows her in an uta-karuta tournament and introducing herself as "Heiji's fiancé", plus there's a picture of her and Heiji's younger selves making a pinky swear.
Momiji has a close personal interest in Heiji's cases as he makes the news. For some reason, she believes Heiji will be her future husband, despite his feelings for Kazuha. She and Heiji did meet as children and apparently made a promise.
Momiji is also extremely smart, especially in regards to catching details that others miss. When Muga Iori informed her via phone some details about a case Heiji was working, Momiji actually caught other signals that Muga himself had missed and used them to reach a correct deduction that would greatly help Conan and Heiji. Muga also implies that Momiji engages in her own detective work at times, as she is no stranger to making such deductions.
Momiji seems to be very girlish and fond of taking some degree of care in her appearance. She had pierced ears and small earrings, and her nails are seen painted in intricate patterns. Momiji also has a notably larger bust size than other girls in the series, flustering Heiji in their first meeting in movie 21, making flat-chested Masumi jealous and baffled when she first sees Momiji, and leading Okita to simply referring to Momiji as "Boobs" in a conversation with Ran.
Finally, Momiji is a champion in the famous card game Hyakunin Isshu Karuta, a game that Kazuha is also proficient in. The movie plot takes place as both she and Kazuha are getting ready for a karuta tournament.
 Plot overview
 Non-canon plot overview
 Heiji Hattori and Kazuha Touyama
Momiji and Hattori made a promise years ago which she still remembers which was revealed to be that Heiji proposed to her. She immediately recognized him, but Heiji at first didn't. She has a love interest for Heiji and even calls him her "future husband". Because of this, Momiji and Kazuha consider one another as rivals and their interactions are laced with one or another degree of passive-aggression.
 Muga Iori
Iori is Momiji's butler and loyal servant. She values that he approves of Heiji as her future husband.
 Soshi Okita
Momiji and Okita are classmates. While talking to Ran, Momiji is annoyed at the mere mention of Okita, whom she calls "that kendo boy", though she is willing to deliver a message from Ran to him. When he later comes over to the crime scene with some kendo buddies to hunt down tengus, Momiji only has sarcastic comments and further annoyance to offer. In turn, Okita doesn't want Momiji to learn of the girl he has a crush on, fearing he would never hear the end of it if she heard of his crush.
Somewhat rudely, Okita only refers to Momiji as "Boobs" in a conversation with Ran, in reference to her overly large breasts.
 Ran Mori
Ran and Momiji have met in the past (see below). They're mostly polite to one another.
 Manga vs. anime
In The Crimson Love Letter, Ran and Momiji met in Osaka, while Ran says in the manga they met the last time she and her dad travelled to Kyoto. Files 33-35 are the first and only time when Kogoro goes in train to Kyoto for a friend wedding, and Ran came along to see Kyoto for the first time, and brought Conan rather than leave him alone in Tokyo. Then, in the manga, Ran meet previously Momiji then or some time off-screen. In The Missing Sweets in the Old Shop and Private Eye in the Distant Sea, not based on the manga, Sonoko was in Kyoto along with Kogoro, Ran, Conan, and the Detective Boys, while in the manga she doesn't know Momiji yet. The movies are not canon and Gosho Aoyama simply omitting their first meeting in the manga doesn't make the movies canon either.
 Name origin
Her name Momiji means "red leaves", and it's the name for the Japanese maple tree. In Japan, the custom of viewing the changing colour of maples in the autumn is called "Momijigari", and Kyoto (the city where Momiji is from) is known for its good momijigari spots.
Her surname Ooka means "large hill", and it comes from Ooka Tadasuke (大岡 忠相). Not only he was a Real Life samurai and magistrate in the service of the Tokugawa shogunate, but has been featured in jidai geki series like Ōoka Echizen and Meibugyō! Ōoka Echizen, among others.
 See also
- ^ Manga Volume 94, File 3 (1002)