Miko, a serious college student, was troubled every day by Nitori, the sloppy older sister living next door. When they met in the morning, Nitori smelled of alcohol from a hangover, and at night, she would interfere with Miko's studies by letting out loud moans while masturbating. Miko viewed Nitori as a negative example to avoid. However, Miko finally reached her limit and went to confront Nitori. That encounter became the catalyst that shattered Miko's values and completely twisted her sexual preferences...