It comes out more in certain sidequests. I don't know if you've seen the script of the Mushroom Road sidequest, but there's a scene where Guy is rude to Asch in favor of Luke and Luke yells at him for it. It's quite gay.

He did. I haven't seen any canon to suggest how their relationship was back then, aside from a part where Natalia mentions that Asch said something to her and then went to play with Guy. I think that part of the resentment towards Asch is the Luke thing, but even that doesn't make sense. Guy treats Asch badly when he acknowledges Asch at all, and it's just... weird. On the other hand, Asch does listen to Guy.

-is not on second playthrough... no-