Hare Nochi Munasawagi

The story of Harenochi Munasawagi does not start in a very original way: the protagonist is a high-school boy named Kazuhiko, who is - surprise! - permanently horny, displaying his "affections" at any given opportunity to anyone young and female, including even his childhood friend Chihiro. But while the focus on the story is on Kazuhiko and his quest for physical intimacy (which often results in girls getting angry and beating him up), there are other rather disturbing elements that come into play later - in particular, bunny-like demons who share Kazuhiko's passion for the opposite sex...

[From Moby Games]