I don't think there's a perfect way to do it since that would rely on Lucas/Isak not being just a teenage boy that doesn't know everything. He doesn't know the situation with the girls, if he did I'm sure he would never have told her to talk to them. And he's just figuring out his own life, these things take time.
Their friendship though, one of my favourites, especially in skam france since they screwed over a lot of the rest.
Their ig picture.
