After two years with his girlfriend, they respect each other and have satisfying sex, yet he still cannot bring himself to propose. He suspects his buried sadism and fragile pride are holding him back. When he visits her family home, her mother Kaori warmly welcomes him. While his girlfriend is away, he confesses his doubts about marriage, and Kaori gently accepts his feelings without judging him. Her easygoing compassion only gets under his skin, prompting him to unleash all his pent-up frustration and sadistic urges on his girlfriend's mother.