tbf it is kinda skippable in pb1. And the boyfriend does lots of cheating as well.
And I am not sure what people actually mean with cuck/ntr. Because it basically only means cheating or being cheated on. But the meaning seems to be shifting to a threesome where the cheaters have the sex and the cheated has to jerk off and or be humiliated.
There is even a scene in pb1 where he has fun with another girl and she watches and masturbates.