Sumire was so horny that her boyfriend had to break up with her because of it. One day while looking for something in her younger brother Kazushi's room, she found an unused massage coupon he had made for her years ago. Their parents were out on a trip, leaving them free to indulge their desires. While masturbating, Sumire discovered Kazushi masturbating outside his room. Remembering the massage coupon, she decided to present him with a new one, this time using condoms since they seemed like they could be used multiple times. With their parents away, the siblings were able to fully express their sexual desires without holding back.
