Matarou, a young boy at school, confesses his feelings for his only girl, only friend, only cousin, only niece, only sister, only daughter, only girlfriend, Mikoto. She invites him over to her house for dinner. While she's making dinner, Matarou looks around the house and collects pieces of Mikoto's diary. As he continues his strange quest, he slowly realizes that Mikoto isn't what she appears to be.