[She shifts a little, face not so pressed into his neck so that she can talk.] Allen is an exorcist. They all have the ability to use something they call innocence which...sounds weird and has nothing to do with actual innocence as far as I know.
Anyway...
Sometimes it's just a weapon. Like Cross' gun. His kind is harder. He was born with it. It's a part of him. His arm—the red one—is a weapon. [You see how they bonded early on? Not a mutant, but something close.]
He has to fight the akuma and noah because most people can't. It's dangerous. [And there's more. The worst of it. She's not sure she should share it though because that's Allen's secret and not being here doesn't mean he won't come back.]