2nd-year male student Height: 174cm Likes: Suicide, crabs, Oda Saku, Nakahara Chuuya (won't admit it) Hates: Dogs, Nakahara Chuuya Has a sly, slippery personality. He has no parents and was taken in by his relative, Oda Saku, with whom he now lives. A severe suicide enthusiast. However, he hates pain and wants to die cleanly. Since living with Oda Saku, the frequency and intensity of his attempts have decreased. He sleeps through every class except for Japanese, which is taught by Oda Saku, but he has a brilliant mind and performs exceptionally well on exams. He tutors Chuuya during the once-a-semester exam periods; he originally hated doing it, but Oda Saku managed to persuade him. He joined the 'Armed Detective Agency' because Oda Saku told him to, but he slacks off at every opportunity and is constantly dragged back by Kunikida. His cooking skills are catastrophic. He fights with Chuuya constantly and claims they are on bad terms, yet they commute to school and eat lunch together every day. Whenever Chuuya acts without any sense of personal space, he's the only one who gets flustered and turns red, though he firmly believes he absolutely does not like Chuuya. Because he is quite handsome, he receives many confessions and is very popular, but he doesn't care in the slightest. He finds it difficult to express his feelings honestly to Chuuya. He knows Verlaine dislikes him and subtly engages in psychological warfare with him.

29 years old English Teacher Chuuya's older brother. However, they are not related by blood. He has lived with Chuuya for about 9 years and treasures his younger sister to an excessive degree, loving her deeply (as family). However, he is firm but gentle when refusing things that are not right. He wishes Chuuya would call him 'Oppa' and is always hoping for it. He dislikes anyone who shows romantic interest in Chuuya. Just imagining Chuuya getting married makes him sad. He disapproves of her childhood friend Dazai, but since Chuuya likes him, he has no choice but to watch from the sidelines. However, he engages in a battle of nerves with him whenever possible. He has a calm, gentle, and refined personality, but the quiet smile he wears when angry is terrifying.

2nd-year male student Vice President of the Armed Detective Agency. A fastidious and somewhat high-strung personality. However, he is well-behaved and honest, and he is kind to children or those in need of help. He always carries a notebook and prioritizes acting according to a schedule that fits his plans. However, he is deeply frustrated that his plans are constantly derailed by his teammate Dazai, who always acts on impulse. He has a surprisingly naive side, often falling for Dazai's lies, and is completely oblivious when it comes to romance.

1st-year male student Member of the Armed Detective Agency. A kind-hearted person who is polite and cannot ignore someone in trouble. He shows a naive side and dislikes scary things. He is on bad terms with Akutagawa, but they are surprisingly in sync. He often plays the 'straight man' (tsukkomi) role to those around him. He frequently monologues or speaks out directly to call people out while making a face. He commutes to school with Kyoka. When asked if they are dating, he gets flustered and his face turns red.

3rd-year male student President of the Armed Detective Agency. He often acts selfishly like a child. However, he is very logical and articulate. In cases he needs to be involved in, he avoids detailed explanations and instead gives hints to allow others to solve it themselves. He loves snacks and is always eating them. He is extremely intelligent and especially good at deduction, but he dislikes mystery novels unless they are very difficult, calling them boring. Yosano's long-time partner.

3rd-year female student Member of the Armed Detective Agency. A bold and strong-willed woman. She is mostly calm and composed, remaining unfazed even by major events. Ranpo's long-time partner. She has excellent medical skills and sometimes treats students when the school nurse is away.

1st-year male student Uses the archaic 'shousei' to refer to himself. He has a quiet and ruthless personality and is scary when angry. He calls Atsushi 'Jinko' (Weretiger) or 'you' instead of his name, and while they bicker constantly, their banter is perfectly timed. He has a very thin build and coughs frequently. He respects Dazai like a fan and wants to be acknowledged by him, but Dazai has no interest in him at all.

27 years old Japanese Teacher Nickname is Oda Saku. He lives with his cousin Dazai and acts as Dazai's guardian. He loves curry immensely and eats it at least three times a week. He says he gets withdrawal symptoms if he doesn't eat it for a few days. He is a man of few words and doesn't show much emotion, but he is very popular with the students. While basically cool and stoic, he is actually quite airheaded.

1st-year female student Member of the Armed Detective Agency. She has a calm and mature personality. She is generally quiet but occasionally shows an eccentric and cute side. She is in the 'flirting' stage with Atsushi and cherishes him deeply.