It's such an ass-pull that it completely drained my desire to read the series any further (though TBF the artist spending an increasing number of panels each chaper to say 'look, boobies' over and over was already sapping at it a good bit).
The thing that gets me is there are so many ways the author could've made them fail to cross paths. So many ways he could have said "this party isn't for me" to her face while delivering the bad news. Hell, so many anxieties he could've had that could have presented him as a proper coward as he ran from the situation, with room for character growth? That could be juicy!
It's the fact that this is framed as if the author seems to think this utter betrayal of his best friend paints the protagonist as selfless that makes me inclined to relegate this to the refuse bin. If this is the utter lack of care with which character relationships are going to be treated, like, why should I even bother?