Quote Originally Posted by poopdeville View Post
Well, I mean, he didn't "borrow" from his future.
And how do you know that?

The only explanations we've had to far are Pitou and Killua guessing what happened.

I think he temporarily swapped bodies with his future self. I think it'll wear off, and he'll go back to being a kid, and his future self will probably be stuck missing an arm.