Rio and I are not real siblings. Rio was the child of my father's second marriage… After that, we lost both parents and have been living together by combining our sibling powers. Rio, who was so small back then, has now grown into such a beauty. I had feelings for this stepsister… I confessed this forbidden love only to my best friend, Kenichi. But that was a mistake. Knowing my feelings, Kenichi forcibly started dating Rio and showed us obscene sex in our home that drove us nearly insane…
