Toshiya's stepmother, Yui, who usually gives up on everything quickly, has suddenly become obsessed with exercising. She claims it's to tighten her sagging waistline, but Toshiya expected her to get bored soon. However, when he went to check on her half-teasingly, he found Yui's sweaty body looking strangely erotic. To his surprise, her drenched appearance turned him on. Sweat trickled down her nape and through her cleavage... Unable to suppress his excitement, Toshiya instinctively reached for his crotch...