To put it plain and simple, any scenario where Annerose gets raped is a bad-end scenario. This game is fairly unique because the MC isn't a girl but rather a guy who wound up wrong place wrong time and wound up as the heroine MC's (Annerose) zombie slave, but after getting bullied enough by her tries to get her to fall in love with him (via mass amounts of sexual harrassment).
Basically at several points of the game there's choices to make, where if you make the wrong one, Annerose gets raped, and it's a bad ending, eventually you can make it to the very end of the game and if you still made too many wrong choices, you get the same bad ending the animation adaptation gave us.
Outside of Annerose there's some unavoidable rape scenarios, but if anything it's basically shutting down the possibility of a harem (Annerose is the focus, afterall) and it's possible you can miss getting the true ending, though iirc getting that is just picking a few choices that show you care about Annerose more than the other 3 girls before having sex with them.
All in all it's a pretty good game that's kind of separate from BL standard because the male MC isn't evil (though he's quite mischevious in taking Annerose's virginity and eventually making her his) and most of the rape scenarios can be avoided as those are actually bad ends.