No one asked for that, it was clear from her first meeting she was an easy going party girl.
But rape and abuse for years on end just doesn't fit her character, even less in the rest of the story.
If you use such heavy drama the least i expect is, that her past and trauma, as well the overcoming of that, will be a central point for that character (not that this MC would be any help with anything else as taking care of the bad guys). But this is just cheap drama for drama's sake, so the MC can save her from some rapists...she's a party girl, way simpler ways to do that.
Dark story ? I wouldn't call it that, besides the MC's past.
The rest of the game is the MC helping all LI's (mostly beating someone up) and the girls falling in his lap, completely fine to share him with the other girls...
Thinking about it the backstory is not even that "dark" unless you really only play "vanilla incest sim" games. The MC was groomed absolutely but he was never brainwashed lol, in exchange for being groomed/trained (was he even abused by victor?) he was taken off the streets where he had absolutely nothing as a young child. Unless I am mistaken he was already a Gary Stu back then and was the "top of his class best ever etc etc"
not to mention for the last few/several years he was having sex (which obviously started with dubious consent) with the hot goth daughter
Edit: Another blow to this games "dark themes" is that the VERY FIRST TIME that MC has feels for someone he overcomes the grooming and resolves to betray victor