I’m dating my coworker Saeko, but she refuses to have sex with me because I’m still a virgin. When I try a dating app, I unexpectedly match with her married older sister Mariko, who is sexually frustrated while her husband works overseas. We agree to keep everything secret and become fuck buddies. Unlike my girlfriend, Mariko even lets me creampie her, and the sex feels so good that our desires keep escalating until we start secretly fucking at home too.