- Houtarou Oreki: The protagonist of the series, a passive and calm boy who seems to always "conserve energy" and never exerts effort on anything unless absolutely necessary. He is often forced to solve various mysteries to fulfil Eru's requests.
- Eru Chitanda: An inquisitive and energetic girl who joins the Classics Club for personal reasons. Whenever a mystery is brought to her attention, she is unable to stop thinking about it.
- Satoshi Fukube: Houtarou's friend who joins the Classics Club with him. He has very good memory, which allows him to call himself a "database". However, he does not have logical thinking skills, therefore he is unable to solve mysteries like Houtarou.
- Mayaka Ibara: The fourth member of the Classics Club. She attended the same middle school as Houtarou and Satoshi. Although sometimes she is impulsive and stubborn, she is responsible girl. Her hobby is reading manga, as well as creating it by herself. Mayaka has had a crush on Satoshi since middle school.
- Tomoe Oreki: Older sister of Houtarou. She forced him to join Classics Club.
- Tomoko Oohinata: New temporary Classics Club Member
- Masashi Toogaito: President of school's Wall Newspaper Club.
- Kaho Juumonji: Eru's friend and shrine maiden at Arekusu Shrine.
- Fuyumi Irisu: Director of class 2-F amateur film; plays vital role in corresponding arc.
- Junya Nakajou: Assistant director of class 2-F amateur film.
- Tomohiro Haba: Props master of class 2-F amateur film.
- Misaki Sawakiguchi: PR manager of class 2-F amateur film.
- Shouko Yuasa: President of the school's Manga Club.
- Ayako Kouchi: Prominent member of the school's Manga Club
- Youko Itoigawa: School's librarian.
- Omichi: Math teacher.
- Masakiyo Ogi: English teacher of Houtarou, Mayaka and Satoshi during their middle school years.
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