[He's never had someone lord it over him quite like this before. It is dawning on Natsume that yes, it is about the grape thing, though. He doesn't roll his eyes since Kazuya is taking it so seriously, and he really does feel too tired to get into an argument over it.]

I'm sorry, and I'll try to remember acting like that isn't playing around to you. But I do think of you as a friend along with everything else.

[He doesn't make contracts just to be his friend, right? Natsume does look genuinely contrite. Also a bit like a kicked puppy.]