"Best friend"...? Is he particularly skilled at being a friend?
I suppose someone being as flexible as he would make them good company...

[If they sound like they've never heard of best friends before, that would be because they haven't. The concept doesn't exist to them.
They didn't even have any normal friends until they, y'know, died. Right now, they still refer to everyone in Everhood as acquaintances or colleagues...]

... It makes me glad to hear you have someone you cherish so, however. As embarrassing as it feels to admit, that is something I have yet to experience.
But it sounds as though you two make quite a pair.