Asakura Aiko, who separated from her husband a year ago, lives a peaceful life as a single mother with only one child. The walls of the apartment they live in are thin, and they can often hear the sounds of a man and woman having sex next door. The moans they hear every day are enough to stimulate her son Yoichi's sexual desire. It is only natural that he would awaken to the opposite sex. However, the woman Yoichi has fallen in love with is... his mother.