"Amu", a high school student who came to Tokyo to take an exam in Tokyo.Her place of acceptance is the "Kawasaki family", a relative of "Amu". The "Kawasaki family" has a son named "Shintaro" who is a ronin student, but he doesn't study every day and just masturbates in front of the computer and lives an unproductive life.Meanwhile, "Amu" and "Shintaro" meet again for the first time in a while, but "Shintaro" notices that her cousin's breasts are outrageous."Shintaro" remembers that they used to bathe and sleep together in the past, and he can't help but want to see "Amu"'s breasts.