It's exactly what happened as far as I can see. I have no idea why you think you can't work with somebody unless he's your friend. The world is full of people who do. Armed forces are full of people who risk their lives to save mere coworkers or total strangers, not best buddies.

Of course you might also be correct and he's just a terrible tsundere, but there's little evidence of it yet. Since this is anime, based on a light novel, that's quite a high possibility, but I do hope it's not the case. It would be refreshing if "I'm not here to make friends but work and earn money" was, for once, genuine. If this anime had continued for a longer time, I also wouldn't have minded at all if Ranta had found a bunch of people more like his own dark knight kind and switched groups immediately, becoming friends with those others. That would also have been realistic, just like the extreme difficulty of combat and losing members.