After losing her husband, Eriko is living alone when her daughter and son-in-law return home. Eriko feels joy as a parent in the presence of a lively family again after a long time. Tatsuya is nervous around his beautiful stepmother and can't fall asleep. One night, he wakes up and sees Eriko's naked body, hot after a bath, through the slightly open door. The next morning, the image is burned into Tatsuya's mind and he attacks Eriko while she is cleaning... The distance between the two, who have crossed the forbidden line, rapidly closes...