A couple living happily together is suddenly joined by the husband's NEET brother, who moves in after being kicked out of his parents' house. After seeing her husband off to work and finishing the housework, Arisa secretly indulges in masturbation in her room. Her brother-in-law catches her in the act and asks for her body just once, and out of embarrassment, she gives in. This act sparks an escalation starting the next day; she is made to give blowjobs to his friends and is teased with a remote vibrator while her husband is right beside her. Despite her confusion, she finds herself increasingly drawn to the insatiable brother's carnal desires.