Mizuho, who lost her husband in an accident for two years. For her young widow, her father-in-law, Honma, asks her to find a good person, but she is worried that when she leaves, only she, her second son Cozy, and a man remain. The day Cozie brought home his girlfriend Hitomi, Mizuho, who was attracted by the groans in his room to peek into the sex of the two. Eventually, she begins to seduce her master and father-in-law to let go of the bond of reason.