Atsushi and his girlfriend Kana are about to get married. They spend every day at her house discussing arrangements for the wedding, but Atsushi is Kokoro as he stares at her mother, Yui... After divorcing her husband, Yui raised her daughter on her own, and Atsushi is genuinely attracted to her strength and courage. One day, while Yui is taking a bath, Atsushi sneaks into the bathroom. There he finds Yui's freshly removed underwear... He instinctively picks it up and smells it, but ends up running into Yui just after she's out of the bath...