I'm All Yours(1991)

Original title: みんなあげちゃう♥

Rokuro, a penniless student living in a run-down apartment, gets a surprise visit by the beautiful and quite mysterious Mamiya Yu. For some reason she has hopelessly fallen for this no-good pervert. As it turns out she is actually the daughter of a very wealthy Japanese family. Considering Rokuro's background, he cannot believe his luck... but not all is as it seems. This rich family seems to be a lot more perverted than even Rokuro could have imagined...