It's a very sensitive topic among certain players that go very far to show their dislike. It's easier to link to what it exactly means as opinions are divided.
https://lewdpixels.com/features/ntr-what-does-it-mean/
This game has like 400 scenes and a bunch of those involve sharing/gangbang/threesome/foursome (MFFF) and other pretty wild stuff etc. But you won't even get to see those if you don't want to and stick to Good Paths which are generally more mellow, MC gets all the girls for himself (Harem) and on top of that has a very(funny/sad) interesting story.
This is what I mean. Coincidentally posted a few hours after mentioning NTR. People don't play the game, see a tag and get angry. Not realizing this game has the most tags out of all games on this platform. They're all optional and one can choose how to proceed in situations. Certain choices change the game in a major way.
50% of the negative reviews on this game are similar to the one above but despite that, this game still scores highly.
Anyway, easier to just mindlessly leave 1-star ratings without playing a 20+ long-hour game that has a shit ton of time invested by a 2-man team.