I think that Torulf never met Arvo, what I really think is that he's interested in trying new things and by that I mean new people... he seems to have some history with Lake (I think they were fuckbuddies) and Arvo seems like just another naive and cute guy with whom he can have some fun (for a while) ... Torulf also seems very reluctant to talk about relationships (maybe he had some troubles in the past?), I imagine his route will have two paths, one where he might overcome his problems (if he has any) and settle down for one partner and the obvious one with tons of casual sex and nothing else.