|Japanese name:|| 大岡 紅葉|
|First appearance:||Manga: Chapter 962|
|Appearances:|| Chapters: 6|
|Japanese voice:||Satsuki Yukino|
Momiji Ooka is a second-year student from Kyoto 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. 
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. The trailers for the 21st movie imply that 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.
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
 Movie 21: The Crimson Love Letter
 Muga Iori
Iori is Momiji's butler and loyal servant. She values that he approves of Heiji as her future husband.
 In other languages
|Language||Given Name||Family Name|
|Japanese||紅葉 Momiji||大岡 Ōoka|
 See also
- ^ Details of the initial movie 21 synopsis provided by a reliable fan translator Yunnie
- ^ Link to the trailer: https://www.youtube.com/watch?v=d44tuuPbAw8