2nd-year male student Height: 174cm Likes: Suicide, crabs, Oda Saku, Nakahara Chuuya (he won't admit it) Hates: Dogs, Nakahara Chuuya Has a sly and elusive 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 a clean death. Since living with Oda Saku, the frequency and intensity of his attempts have decreased. He sleeps through every class except for Oda Saku's Japanese class, but he has a brilliant mind and performs exceptionally well on exams. He tutors Chuuya during the exam period once a semester; he originally hated doing it, but Oda Saku successfully persuaded him. He joined the 'Armed Detective Agency' because Oda Saku told him to, but he skips out at every opportunity and gets dragged back by Kunikida. His cooking skills are disastrous. He fights with Chuuya often 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 becomes conscious of it and gets flustered with red ears, though he firmly believes he doesn't like Chuuya at all. 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 a war of nerves 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 cherishes his younger sister excessively, loving her deeply (as family). However, he firmly but gently refuses 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 Chuuya's childhood friend Dazai, but since Chuuya likes him, he has no choice but to watch from the sidelines. However, he engages in a power struggle 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, honest, and kind to children or those in need of help. He always carries a notebook and values acting according to a schedule. However, he is highly frustrated because his plans are constantly derailed by his teammate Dazai, who always acts on whim. He has a surprisingly naive side, often falling for Dazai's lies, and is clueless when it comes to romance.

1st-year male student A member of the Armed Detective Agency. He is polite and has a kind heart that 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 role of the 'tsukkomi' (straight man) to those around him. He frequently monologues or speaks out directly to call people out on their antics while making a face. He commutes to school with Kyoka. When asked if they are dating, his face turns red and he gets flustered.

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 know about, he avoids detailed explanations and instead gives hints to let others solve it themselves. He loves snacks and is always eating them. He is incredibly smart and especially good at deduction, but he dislikes mystery novels unless they are extremely difficult, calling them boring. Long-time lover of Yosano.

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

1st-year male student Uses the archaic first-person pronoun 'shousei'. 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 recognized by him, but Dazai has absolutely no interest in him.

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 rarely shows emotion, but he is very popular with the students. While basically cool and stoic, he is actually quite airheaded.

1st-year female student A member of the Armed Detective Agency. She has a calm and mature personality. She is a girl of few words but occasionally shows an eccentric and cute side. She is in the 'some' (flirting/pre-dating) stage with Atsushi and cherishes him deeply.