A Boys Love and Hentai series worth adding to your list.
The crisp rays of summer sun find the effeminate Pico embroiled in yet another heated and lustful fling. While out biking, Pico meets and befriends Chico—a lively boy not much younger than him, but leagues behind in the affairs of the flesh. After the innocent Chico shows his sister in the midst of self-pleasure to Pico, Pico takes it upon himself to educate this confused youth.
Plot summary from MyAnimeList. Data and images via Jikan API.