Pretty peculiar take on BSS, it has a netorase spin.
The two are childhood friends, and actually love each other, but since he never took the initiative she got a pretend boyfriend to get his attention; he didn't get mad, it took the opposite effect actually, turns out he has cuck fantasies and is aroused by her doing it with someone else, and she actually has great body chemistry with her boyfriend so she is reluctant to break things up.
Now they are deadlocked in this situation, he calls her up to please show him another video; he pleases himself in front of her, being extremely aroused at how much she is into doing with her boyfriend, she is embarrassed at him for being so into it, and she is actually quite annoyed at how he did not react the way she originally planned, which is to get him mad and try to snatch her away.