NTR is optional, but the main focus of content is on the sharing/adultery paths currently. No harem content that I’ve observed. From the sounds of your questions, you may be better off with a vanilla game of some type, but by all means give it a try.
Viewing post in Let the Nightshine In [v0.1 Chapter 1] [Sieglinnde] comments
let me clarify that I’m not the creator of this game, just a fan. You can avoid sharing/adultery, but there is less content on the vanilla path. The game so far has most of its scenes in the sharing/adultery paths. You do get choices which will yield different results so there is a sense of control over the MC.