It looks like the other thread got nuked for being a duplicate, so reposting the basic guide.
Pick a girl 5 times in the common route to get into her route, then keep picking that same girl for her good end. Pick the other girl a few times to trigger a choice between the bad and netorare ends.
Gotta say, the inclusion of electronic/dubstep music in the soundtrack is goofy, especially when it starts blasting that dark, bass-heavy villain theme the first time the other male character shows up whilst the narration is calling him a good guy and your only friend. And the other guys sprite just looks strange with that (comically) jacked body and muscle shading topped with a super flat, texture-less face.