A "kris" is a type of dagger, and "to off" someone is to kill someone. So Kristoph is actually an appropriate substitute for Kirihito, I think.

(I did look up what a "kris" was just to be sure, it's a wavy-bladed dagger)

According to Webster, the pronounication of "kris" isn't very close to what you'd normally pronounce the name "Chris" and its variations like. And what's become of the "t"? Kirihito/ Hitokiri is pretty obvious, but the "I'll off you with a kris!" seems pretty far-fetched, and I seriously doubt anyone who doesn't know the context could possibly think of it that way.

Hmm, I wasn't aware that the pronouciation was any different... (I did know that a kris is also called a keris, however.) Still, the spelling is "kris", so it could be a visual pun.

As for the "t", that's why I added "TO off". (I suppose to make it more viable, you would have to spell it "Kristoff", but it isn't, so...)