Erica, who lost her husband in an accident this summer, lives with Shoichi, who was her husband's stepchild. Although they are not related by blood, they were actually in a relationship of a man and a woman. Shoichi tried to suppress his growing lust and leave home, but his father passed away just as he was about to do so. Since then, he has tended to stay at home, but one day he was invited to a hot spring trip by Erica.
