I mean, as long as we're defining NTR as cheating. Wouldn't any Roxxy content end up being NTR? Unless Roxxy just dumps Dexter after you beat him at basketball or something, but that's a bit of a lame punishment for such an asshole of a character.
lol i think you do not understand who NTR stand for. So is for that who you are confused i thing.
Let me explain it to you.
NTR is divide in Two category.
1)The most hatred: Netorare
2)And the one who like to also all ppl: Netori
1) Netorare is whan the main character is just a powerless one, you cant do anything. You are forced to see all you girls/woman stolen be another man. Generally in the game there is a bastard one who steal all the girls from the main character. So you play as a MC who just cry, suffer pain and cant do nothing to stop the bastard one.
MC know all, he see is woman fuck with this bastard and just cry! MC woman just see you smile, looking at you and then let this man fuck her/impregnate her and than if she become pregnant, you are forced to raised the child as you son.
2) Netori is when MC stolen all the girls/woman to other man
In this case you are the good and the evil one. You can stolen the woman from other man.
Almost all the time the MC is the good one, who just find the true. For example: MC find that an husband betray is wife. So you angry stolen the wife to the bad man. Some time MC for revenge stolen the woman/girl. Example when MC was young is brother married the woman MC like. So for revenge MC stolen the wife from his brother.
In all the case you are the one who can shaped is destiny.
Look to summertime. The MC in this case are the one who have the controll over all the girls/woman. If you want, you can steal the girl who likes Erik. Or you can help Erik to find a girl and in this case you stolen his mother (but that is cheating only. Because Erik do not know it).
In the Roxxy case is just Cheating on Dexter. MC in this case again is Netori, becouse he steal Roxxy to Dexter. Dexter are the bad boy in this case, because he continuelly bully you. So for revenge MC stolen is girl.
Cheating is another thing.
Cheating is when no one know that you are fucking with another person. But then someone find the true and in almost all the case you lost you love.
Almost all incest game for example are Netori/Cheating
If you play Big Brother for example, that game at the start was a Netorare. But after the fiasco/flop the autor change the playstyle and turn the game in a semi-netori. Now there is no more Netorare in Big Brother. At last till the autor wanna it.
In any case for me. The best choice is Netori. Because the protagonist never gets feet on his head. You are the one who stolen or normally let girl/woman fall in love for you.
I hope I have explained well.