Ron Kamonohashi

Premise

The series focuses on the adventures of Ron Kamonohashi, an eccentric private detective, and Totomaru Isshiki, an unskilled police officer, as they solve crimes together. Five years ago, Ron was the top student at the Detective Training Academy Blue. However, after being found responsible via temporary insanity for a deadly incident known as the "Bloody Field Trip", his detective license was revoked and he was expelled. Unable to fulfill his only love of solving mysteries, Ron has lived in isolation since. When Totomaru seeks his help on a case, the two form a partnership where Totomaru takes the credit for the cases that Ron solves.

Characters

Main characters

Ron Kamonohashi (鴨乃橋 ロン, Kamonohashi Ron)

Voiced by: Yōhei Azakami

Portrayed by: Yuta Kishimoto

A sixth-generation descendant of Sherlock Holmes, and a ninth-generation descendant of James Moriarty. His detective license was revoked five years ago following the "Bloody Field Trip", an incident he cannot remember. Whenever he hears a murderer confess their crime, Ron enters an uncontrollable state where he pressures and convinces them to kill themselves.

Totomaru Isshiki (一色 都々丸, Isshiki Totomaru)

Voiced by: Junya Enoki

Portrayed by: Yutaka Nozaki

A police detective in the Metropolitan Police Department who gains some renown by taking credit for the cases that Ron solves. Ron calls him by the nickname "Toto" (トト).

Amamiya (雨宮)

Voiced by: Yoko Hikasa

Portrayed by: Haruna Ishii

Totomaru's boss in the Metropolitan Police. Although usually cold and serious, she has a crush on Ron, whom she thinks is named "Kamoo" (鴨夫).

Mofu Usaki (卯咲 もふ, Usaki Mofu)

Voiced by: Nao Tōyama

Portrayed by: Marina Tanoue

A renowned neurosurgeon who is extremely clumsy outside the operating room and is always wearing bandages due to her injuries. She concocts a combination of medicines to suppress Ron's "culprit-killing" syndrome, but there are side effects.

Blue

The Detective Training Academy Blue (探偵養成学校BLUE) in England is the world's most prestigious academy for training detectives.

Spitz Feier (シュピッツ・ファイア, Shupittsu Faia)

Voiced by: Taku Yashiro

Portrayed by: Ryōma Baba

The tracking instructor at Blue, who is sent to investigate whether Ron is violating his detective ban. However, his actual goal is to have Ron help him find his missing brother. Spitz befriends Ron and Totomaru and continues to assist them on various cases.

Fin Fennec (フィン・フェネック, Fin Fenekku)

Voiced by: Megumi Han

The locked room instructor at Blue and one of less than 10 people in the world who have an S-rank detective license.

Shachi (シャチ)

Fin's bodyguard and a graduate of Blue. He attended the academy at the same time as Ron. He is revealed to be the M. Family's informant at Blue.

Hirsch (ヒルシュ, Hirushu)

Voiced by: Kenjiro Tsuda

The anatomy instructor at Blue. He has been a suspect in 15 murder cases, with one of these instances being the reason he was demoted to A-rank detective.

Emme Emmerich (エメ・エメリッヒ, Eme Emerihhi)

Voiced by: Kikuko Inoue

The principal of Blue and a friend of Ron's parents. She informs Ron of the M. Family's involvement in the Bloody Field Trip incident, though discretely due to there being an M. Family informant at Blue.

M. Family

The Moriarty Family (モリアーティ家), more commonly referred to as the "M. Family" (M家), is a legendary crime syndicate and the archenemy of the Holmes detective family.

Tiger Dan (タイガ・ダン, Taiga Dan)

Voiced by: Takehito Koyasu

Milo's uncle, whose real name is Daniel Moriarty (ダニエル・モリアーティ, Danieru Moriāti).

Winter Moriarty (ウィンター・モリアーティ, Uintā Moriāti)

Voiced by: Yumiri Hanamori

Portrayed by: Mizuho Habu

The fourth child of the M. Family who specializes in disguises. After failing at a mission, Milo has an assassin shoot Winter, but then has doctors nurse her back to health as she survives the attack. After recovering, Winter splits from Milo, whom she never forgave for killing their younger sister Alice.

Milo Moriarty (マイロ・モリアーティ, Mairo Moriāti)

Voiced by: Yoshitsugu Matsuoka

Portrayed by: Yoshihide Sasaki

The eldest child and head of the M. Family. He killed his younger sister Alice in order to earn that position. After he loses to Ron, Milo is attacked on the orders of the "new boss" of the family. This is later revealed to be Alice, who survived because she tampered with the gun before Milo shot her. "Disappointed" that Milo showed emotion by hugging her and crying after the shooting, Alice plotted to steal the M. Family away from him once she turned 17.

Alice Moriarty (アリス・モリアーティ, Arisu Moriāti)

The youngest child of the M. Family. Initially believed to be dead, Alice first appears in the series under the guise of "Billy Za Gojila" (ビリー・ザ・ゴジラ, Birī Za Gojira), nicknamed "Billy Goji", a top student at Blue who always has various animals on her. She perpetrates a series of murders at Blue, before escaping custody as her true identity is revealed.

World Detective Alliance

Kei Moore Kikuma (菊間・ケイ・ムーア, Kikuma Kei Mūa)

Director of the Japanese Branch of the World Detective Alliance, an underclassman of Ron at Blue, and the son of Kiku, a police officer and friend of Ron.

Media

Manga

Ron Kamonohashi: Deranged Detective, written and illustrated by Akira Amano, began its bi-weekly serialization in Shueisha's online magazine Shōnen Jump+ on October 11, 2020. The series ended its first part on April 30, 2023, with the second part beginning on June 4. The second part concluded on July 6, 2025. Shueisha has collected its chapters into individual tankōbon volumes. The first volume was released on February 4, 2021. As of October 3, 2025, nineteen volumes have been released.

The series has been licensed for simultaneous publication in North America as it is released in Japan, with its chapters being digitally launched in English by Shueisha on its Manga Plus service.

Anime

An anime television series adaptation was announced on December 18, 2022. The series is produced by Diomedéa and directed by Shōta Ihata, with scripts written by Wataru Watari, character designs handled by Masakazu Ishikawa, and music composed by Yo Tsuji. The series aired from October 2 to December 25, 2023, on Tokyo MX, AT-X, and other networks. The opening theme song is "Ikenai Fool Logic" (いけない fool logic) by Unison Square Garden, while the ending theme song is "Lipsync" (リップシンク) by Hockrockb.

Following the airing of the final episode, a second season was announced. It aired from October 7 to December 30, 2024. The opening theme song is "Feedback o Narashite" (フィードバックを鳴らして; "Playing Feedback"), by Humbreaders, while the ending theme song is "Labyrinth" (ラビリンス, Rabirinsu), by Hockrockb.

Crunchyroll streamed the series outside of Asia under the title Ron Kamonohashi's Forbidden Deductions. Medialink licensed the series in South, Southeast Asia, and Oceania (except Australia and New Zealand) and is streaming it on its Ani-One Asia YouTube channel for its Ultra subscribers.

Stage play

A stage play adaptation ran from November 1–4, 2024, at the Nippon Seinenkan Hall in Tokyo, and on November 9 and 10 at the Sankei Hall Breeze in Osaka. It was written and directed by Keita Kawajiri, with music composed by Futoshi Arai.

Reception

In June 2021, Ron Kamonohashi: Deranged Detective was nominated for the seventh Next Manga Awards in the Best Web Manga category and placed 14th out of 50 nominees. The series has been recommended by mystery writers Rintaro Norizuki, Masaki Tsuji and Sako Aizawa, all of whom have topped the Kono Mystery ga Sugoi! list. In a blurb, Aizawa called the series an "authentic mystery manga for the new era" and praised its fast pace, as well as the tricks and logic used to identify the culprits. Ryoko Fukuda of Real Sound compared the relationship between Ron and Toto to that of the straight man and funny man roles in manzai comedy, and said she was looking forward to how the "pop, fast-paced story" would develop.