Hello! Thanks for asking. There is no NTR whatsoever. Regarding multiple relationships, since it's a harem game, the core idea is interacting with and winning over different girls at the camp. While you can technically build affection with multiple characters, it's designed around the harem genre rather than traditional cheating or betrayal. Hope you give it a try!
...P.S. I'm not a fan of NTR either, (Sondev)