My beautiful sister and I, who should never be able to touch her, are stepchildren who are not related by blood... On a summer day, when the two of them, who have lost their bondage as siblings, fall in love with forbidden creampie affairs.

When the sounds of cicadas began, summer began, and my sister Ayame and I had returned to my parents' house on my 17th anniversary. I went back to my parents' house every year because my older sister, Ayame, had the presence of me. She is a kind and admired sister who took care of me in place of my mother, who passed away early on. Although they are both married, I still have more special feelings for my sister than my family. And on the night the memorial service was over, I was summoned by my father, who had a solemn look on his face, and he was confided that we were not real siblings...