Yuki Osanai

A female student at Funato High School. She has a tonsure hairstyle, is short, and looks very young. She has been acting together with Jōgorō since their third year of middle school, forming a "mutual benefit relationship" with him and aiming to become ordinary citizens together. Normally, she is quiet and shy, a reserved woman who is even more committed to behaving like an ordinary citizen than he is, and often looks at Jōgorō with disdain when he wants to solve mysteries. She has a strong liking for sweets, becoming talkative and showing a joyful expression when the topic arises, and she displays extensive knowledge about local sweet shops and sweets in general. Outside of school, she wears distinctive fashion and always wears a hat as a "disguise."

Behind her aforementioned personality, she harbors a love for "revenge" just like her love for sweets, never forgetting the wrongs done to her and possessing a vengeful nature that seeks to return the favor manifold. She has the action and sharp intellect to match, and when she decides on revenge, she uses everything at her disposal to trap her opponent in cunning schemes, causing deep social and psychological damage. Because of such behavior, Jōgorō describes her as a "wolf."