*spoiler alert*
Well, according to the novel. Inseob(peter) was already in love to wooyeon(philip)when jennie started to tell him stories about philip in their highschool era. Peter got curious and they met at the korean language club, there philip who was an ignorant teenager got close to him but he was born a psychopath who did things out of neglency, so peter fell in love but afraid to tell jennie and to admit himself, it goes on along with jennie's mental illness. Plus philip seems didn't even wanna care about peter's existence
. The problem between them was always the guilty inseob feeling for falling for wooyeon, wooyeon was just there living ignorantly and being possesive over inseob
Oh yes I can definitely pick up on all this from the chapters! I know well that Inseob is in love even when they were overseas. He himself is just not acting with any sort of honesty. Everything he is doing, under the guise of it being for Jennie, is his own selfish desire. But the guilt is constantly following him and he'd have to come to terms with that first. He needs to lay things to rest and realize he doesn't owe Jennie anything.
IT HAS A NOVEL?? WHERE??
Yeah, honestly. He is hiding behind his vows to Jennie. He's saying what he's doing is out of hate for the guy but it really doesn't hold up. Throwing away years of your life on revenge with motives that flimsy? Immensely unlikely. Doing so because you're in love? Well, love makes people do stupid things.