Onee-chan no Kawari ni Nuite Agemasu ~Kanojo no Imouto wa, Shikatanai Kara to Zettai ni Yarasete Kureru~ The Motion Anime

The main character of the hentai, Uchiha Kyouya, is upset that he still hasn't lost his virginity with his girlfriend Mikuna. He turns to her younger sister Moeru for advice, who is his masturbation partner. Earlier, they promised each other to become true mentors for each other and together conquer the difficult path of masturbation. However, everything happened because Kyouya caught Moeru off guard while she was masturbating and sniffing his jacket...