... then it's also falling under NTR umbrella. At least here. I'm commenting on this specifically because there's this common trope that I don't understand. That is that the cuck is clueless to the point of idiocy. The game is absolutely obvious about what's happenning and yet the MC doesn't get the hint, and is not jealous (because how can you be jealous if you don't suspect infidelity?)
Also fem MC cheating on her BF can also be tagged netorare. Or, let me rephrase. Not can be tagged. Have been tagged. So let's not pretend these tags have good, enforced definitions, at least right now.
I'll just go with this one to reply. So many answers up to this point, and as usual, everyone has their own ideas about what it means lol. I'm not directing the next portion to anyone specifically. Just some food for thought for anyone interested.
Have you noticed that the vast majority of NTR games from Japan indeed does feature a clueless male? Have you noticed a very large number of them feature the female protagonist even? Are you thinking that these Japanese people have no clue what the fuck they are talking about? But maybe you are the one that don't quite understand what their angle is with this brand of stories where a clueless guy is getting his girl stolen throughout the story?
If we get down to it, netorare is dealing with the immorality, betrayal, and corruption of the woman. Whether the player chooses to self insert as the cuck, or just use him as a cursor and plot device, his role is basically just to be the one getting cheated on. In most cases he doesn't know until the ending sequence, because most netorare stories are not about the cuckoldry fetish that is popular in the west. The focus is on the
woman. The way it differs from straight up cheating is that her cheating is initiated by the antagonist. She doesn't seek him out to cheat initially, but is corrupted by whatever means into cheating willingly later on. You could talk about Netorare Type A or whatever vndb wants to do, but there is a reason that you don't see very many Type A stories from Japan. It's an off shoot of the genre for them. The vast vast majority are Type B which are about the girl being corrupted. You could also say that whether she cheats willingly or not, it's still cheating, and you'd be right. But netorare is a more... focused and prolonged story arc, more than any single act of cheating itself.
As you can see, netorare, cheating, unwilling cuckoldry, etc etc, they all kind of blur together. It's understandable to be confused, but the simple and most consistent way to view netorare is to just think of it as a corruption story where a female is subjected to the corruption arc by the antagonist and eventually falls completely by the end, throwing away whatever bond she had with her loved one prior to the story. There are of course variations, but we can look at the majority in the genre and come to some understanding about what is driving this fetish.
And what's more, the things that being stolen, or broken, is the bond between two people. Actual couples obviously share a romantic bond and expectations of faithfulness, but netorare doesn't limit itself to strictly romantic bonds. Close friendships and familial bonds being common ones.