Story
After school, Akira Sakagami is about to ask his classmate, Nana Shirayuki out on a date. It was good until she called out to him, but he was interrupted by the appearance of his sister Rio. For Akira, Rio is not only his sister but also his first love. Rio used to live alone, but due to a housing situation, she has now returned to her parents house with Akira. When Akira is told by Rio that Shirayuki looks like her, he sees Shirayuki and Rio in her. That night, Akira is seen masturbating by Rio.
Synopsis via AniList (English).
