Riho, with her overwhelming libido, gets dumped by her boyfriend because of it. Meanwhile, her brother Takel quit his job due to bullying and has been staying home ever since. Ten years ago, Riho finds a handwritten back massage coupon given to her by Takel and comes up with a brilliant idea to cheer up her listless brother while also satisfying her own desires. She shows him the coupon, saying it's a repayment for the past favor, and hands him ten condoms. "As a thank you for the back massage coupon, here's a pussy pounding coupon. Use this to perk up," she propositions Takel.
