Miku is a perverted mother who constantly fantasizes about male genitalia, getting aroused by her stepson Kaoru's underwear and indulging in masturbation during daily routines. Even while folding laundry, she finds her gaze drawn to Kaoru's underwear, losing all self-control. Noticing her intense stares, Kaoru takes advantage, coercing her into a sexual relationship under the threat of exposure. Word spreads, and even her stepson's older brother begins developing an interest in Miku.