What was supposed to be a hot spring trip with just his wife turned into an unwanted threesome when his wife's younger sister, Ena, tagged along, much to Shinji's displeasure. However, after his wife suddenly left due to work, leaving the two alone, she confided in him about something… This marked the beginning of their growing closeness. Unable to resist her persistent advances, they ended up having sex. Since they hadn't had sex in a while, Shinji told himself it would be just this once. But Ena, paying no mind to his reservations, slipped into his futon…
