When I was little, my parents remarried and my little sister Ichika was born. She adored me and was very attached to me. Ichika was a friendly girl and got along well with my friends, which I thought was nice, but I never imagined that she was playing dirty games with me without my knowledge! My cute, my only little sister! They took advantage of the fact that my little sister was still indifferent to sex and took advantage of it! "Let's do it, big brother," my little sister said, and something in my emotions changed...