Heart Triangle OVA-1 / Triangle Heart: Sazanami Joshiryou

The hentai "Heart Triangle" is based on the visual novel of the same name with the prefix 2 from the studio "Ivory", released in 1999. 

The main character works in a women's dormitory as a manager. Well, he doesn't really work, he's just substituting for his aunt while she's resting abroad. Many girls and one guy - in each episode he starts romantic relationships with one of the heroines...