Something similar to Cappuccino, in the sense that the main character moves on from the cheating, and the character who is cheated on (can be male or female and the demographic can be any (shonen,shoujo, josei. sienen) doesn't go back with the person who cheated, that's probably the main aspect. What would be a plus if it was longer than 2-3 volumes.

Similar ones also Skip Beat

Oh, and I have checked the forums, just noone's specified these kind of terms.

There is a pretty simple reason why it's rare to see people use those terms. It's because most people recently seem to like to use the term "NTR" like a fangirl, throwing it out there whenever there is cheating or any type of main character's lovers going to someone else. So instead of "omg he cheated on him or her!", it's "omg NTR!!" or "it's going NTR route." Something along those lines.

Ye kinda annoying, "Omg NTR!" yet it's not NTR, though that said I still even using the term NTR couldn't find anything.