Osanai is a minor supporting character in the anime film Whoever Steals This Book. Osanai is one of the children who attend the Mikura Dojo, the judo dojo owned and operated by Ayumu Mikura, the father of the protagonist Mifuyu Mikura. Along with several other young students, Osanai belongs to the small group of children connected to the dojo who appear in the everyday life of the town. Osanai's role in the story is limited, and the character is defined mainly by this association with the Mikura household and its dojo rather than by any individual narrative focus.