On a summer day when the sound of cicadas was noisy, I returned to my parents' house for the 17th anniversary of my mother. It was the presence of my sister, Riho, who made sure to go home every year. She is a longing sister who has been taking care of me for my mother who died early. As an adult, my sister and I are married, but I still have a special feeling for my sister that is different from my sister and brother. And on the night when the litigation was over, I was called by my father to talk to me, and I was confessed that I wasn't my sister, Riho, and my real siblings ...