Lemme get this straight. Your Love interest is fucking other dudes and you think this isn't NTR? Hahahahahaha wow. Chika is a whore. Fucking other men. She replaced 2 other LI's so the dev could add NTR. There isn't anything special about her story. Nothing to feel sorry for. She could of left, told the people at school what was happening but instead she kept doing what she was doing because she quite clearly enjoys it.
I do love me some grade A cucks. This dev said it was a vanilla harem game. It's not. Once you add 1 girl getting fucked by multiple dudes, who is a love interest, it's NTR. Also she doesn't have to fuck someone in front of you to be NTR. She comes out a love hotel with another guy after getting fucked. That's still NTR. If other people can handle her past they're into getting cucked. There is this great saying. Can't turn a hoe into a housewife.
The dev decided to add this hoe and removed 2 other LI's because they're into NTR no matter what way they try to spin it. This isn't a Vanilla Harem that they said the game would be. It's Harem/NTR/NTS.