Assault on a younger sister suffering from the amnesia and her counselor! Her immature undeveloped body gets thoroughly developed into the full woman. A submissive sister heroine Hikari and her counselor, Aoi, who keeps an eye on Hikari However, Aoi cannot go against the main character, for a very good reason. Aoi must face the main character who assaults Hikari. She is troubled because of this dilemma. As a compromising solution, she decides to surrender her body to the main character.