The girl in Erotica can become an LI (or at least have an ending), but as long as you say no, the NTR never happens.
Hoping it's OK to mention other games in this instance, since they all DK.
IIRC correctly (been a while)
Pine Falls (only some lesbian stuff, and none with LIs)
Rosewater Manor (nothing at all I can remember)
Nursing Back To Pleasure (One LI is married, but you never see anything).
Lancaster Boarding House (one LI has a boyfriend at start, but you don't see anything), there is also a scene with an LI (MMF) that you can avoid. Can't remember if you can avoid her scene with another man completely. I never played her. It's
Rose. None of the 4 girls I played had any problem.