Katsuhiko and his wife Azusa have a cold married life. Katsuhiko's permissive and half-hearted sex makes Azusa more and more sexually frustrated. One day, Azusa is caught masturbating by her stepfather, Yuzo. From that day on, Yuzo starts to play with his stepdaughter's aching body. Despite Kokoro of refusal, he relentlessly teases her sensitive parts and makes her cum...