The guy wasn't necessarily wrong, the MC was too deep in his own insecurities and just being an overall loser, not even willing to fight for the girl he loves until he finally felt threatened.
Really the only problem with the other guy is the fact that he felt that since he worked hard, he deserved her, even though she liked someone else...but at the same time, love isn't logical. If you fell in love with a girl but find out she has a bum for BF, are you not supposed to feel like she can do better? Even if you wish that "better" is you? It's obviously self centered but that's just how love is I think.
At least it was the last push the MC needed to stop being a little bitch boy. I'm an introvert too but the level of introvertedness in manga is just kinda cringe sometimes.
