My college student son begins calling Aiko, his father's new bride who is only two years older than him, "Mom." Living together under one roof, the son gradually becomes drawn to his stepmother's beauty and gentle nature. Unconsciously seeking physical closeness, he starts closing the gap between them. Their relationship slowly takes a forbidden turn through intimate acts such as blowjob, bathing together, and sexual intercourse. Within the confines of their household, a taboo bond develops between stepmother and stepson, deepening through this illicit affair and ultimately culminating in mother-son intercourse.