-.- was that really necessary? It's so hard to suspend disbelief that any one person would actually act like this in the MC's shoes
To be honest, I have this same mindset. Granted, he replied to Izumi in the most insufferable way ever, but I get the comfort of being alone. You just don't have the confidence you can keep up with a relationship and rather self-depreciate to avoid taking a "risk" under some self-righteous idea(e.g. I'm saving them from being with a loser like myself). His attitude is mostly to try and rebuff her intentions, so she can get tired or angry at him and willingly leave him. That way, when she does, he can justify that his whole life of being a loner wasn't just him not making the effort to establish connections with people; that it was everyone else who didn't like or want him around.