Six months into their relationship, Hiroshi visits his girlfriend's home, only to discover her father is abroad on business and her mother has remarried—meaning he's meeting her new stepmother for the first time. As it happens to be the stepmother's birthday, he joins the two women in celebrating together. That night, the gift his girlfriend gives her mother turns out to be unexpected: imported women's lingerie. By chance, Hiroshi catches sight of the stepmother trying it on. The sight leaves a deep impression on him, sparking unexpected desires that begin to grow.