With the story of HH and the connection between the MC and every girl (Ellen and side girls included) and how you get an occasional attack from the outside public, the MC has enough to deal with. A broken heart shouldn't be another issue. Besides I can't see NTR working for Lin, Android, or Ashley. In all of Lin's 300+ year life only two masters have been consistently nice and only you have shown love towards her. I don't think she would risk being sold ending her first loving relationship for a "fling". Android would literally shoot her offender. Ashley's attachment to the MC is at first yandere levels of commitment, even though she has calmed down I can't see her doing this without stabbing her offender to death. NTR in my opinion shouldn't exist. A genre meant to ruin a loving relationship is beyond me. Why people like being cucked is a real mind fuck. Also, if NTR is being caused by blackmail it's the same as rape.
I couldn't agree with you more, the way the relationships were formed yesterday the girls are sentimentally linked to the protagonist makes it practically impossible to place this genre, not to mention that what I like most about this game is the sentimental charge that characters like Lin and Ashley carry , who are my two favorite characters, adding NTR would destroy the beauty of these relationships, it's like I said, this genre only serves to cause disgust, discomfort and anger all kinds of negative feelings, I guarantee you get excited about another guy getting your girl ...that's not healthy, go to a psychologist, please.