Also the name of the dude in urotsukidoji (a hentai movie)
The chojin is a boy who literally turns into a giant sex beast and rapes every woman he sees. In the film he actually destroys a town with his penises (thats right... plural!)
AND he is the hero of the story!
You call someone a chojin if he is very popular with the ladies (1) or gets drunk and lets his labido take control, (although not actually raping anyone or destroying any towns)(2)
(2)"God man.... I got totallycrunk last night and went totally chojin! "