At the beginning of summer, when I heard the sound of cicadas, my sister and Ayame returned home from my mother's 17th birthday. I return to my parents' house almost every year because of my sister, Ayame. She is a sweet and longing sister who has taken care of me in place of my mother who passed away early. Both of them are married, but I have a special affection for her beyond my own family. And on the night when the trial ended, my father called us with a mysterious look and admitted that we were not biological siblings.