@daniel345 you're a huge NTR fan? I'll never understand this love for cucking and shit. I do find people who enjoy that extremely off lol and I'll kink shame that till the day I die.
But aside from that, the thing is the hero wannabe bitch, whatever his name was, was an idiot and an asshat to be fair. He was really hypocritical and hid behind an air of superiority and elitism. I don't give a rats ass for people like that, most people would say such people get what come to them. If that happened to be the actual MC, then I wouldn't feel like it would be a cuck, I would feel the MC deserved it. First of all, it wasn't like the girl ever professed her feelings for him or ever said she'll commit herself to him, the party, or anything of the sort. From the beginning of the manga, it showed that she cared mainly for Hajime ever since the beginning, and her close friend knew that. So even then, I wouldn't call it a NTR even if the hero wannabe happened to be the MC. If anything, with such an unlikeable MC, I wouldn't even be keeping up with the manga.
I do agree though her leaving her original party could have been done better, and the way it was done was pretty bullshit. But Hajime rarely ever seems to want to bother with explaining anything at all, and the mangaka seems to just leave it at that, so I guess it is what it is.