[Reducing Mosaic]JUL-587 The beautiful sister whom I absolutely shouldn't lay a hand on and I are step-siblings with no blood relation... After losing the sibling bond, the two of us indulged in forbidden summer days of intercourse and adultery. Fujimori Riko.

On a summer day when cicadas were loud, I was returning to my parents' house for the first time in a while on the 17th anniversary of my mother's death. The existence of my older sister, Riho, was big in making sure to return every year. She is her longed-for older sister who took care of me all the time in place of her mother who passed away early. My sister and I are both grown up and married, but I still have a special feeling for her sister that is different from her siblings. And on the night after the memorial service was over, I was called by my father to talk to him, and I was told that I wasn't a real sibling with her older sister, Riho.