Well, basically the boyfriend is not even a beta male, he's just straight up from a PG13 visual novel, somehow he landed a bombshell that has her own needs.does this have any hard ntr? not vanilla "teheh sex is good xD" ntr but like humiliation/belittling and the woman just being a terrible human to the person she's cheating on treating him like a wallet or trash? also any gaslighting of him?
The main guy is an "ugly bastard", that is not actually a bastard, is arguably not ugly and that has in himself more spunk ( ) that anyone would think. So he actually start romancing aggressively the girlfriend.
Of course, it may not be pretty 'cause the boyfriend is totally oblivious to this, but the writers did a good work in make it clear why he had it coming.
There are a couple of route change later on the game that can twist radically the content of the scenes, but you must willingly walk into the route change.
If anything, it's interesting that this is one of the few games of this kind where there is no real MC. You manage which events happen but the more or less variable change of PoV make it clear you are just observing the events.
They made a good job on that.