Yui, his stepmother who gives up after only three days, has started to get into exercise. She says it's to tighten up her flabby midsection, but Toshiya knows she'll get bored of it soon anyway. However, when he goes to check on her, half-jokingly, he finds Yui with a strangely Yui, sweaty figure. Toshiya is turned on by her sweaty appearance. Sweat trickling down her nape and cleavage... Unable to contain his excitement, Toshiya reaches for her crotch without thinking...