User blog comment:Mnzombie/Issei's Peerage/@comment-5185939-20120620162733/@comment-4311395-20120711200227

The worth of an Evil Piece depends on the user, Issei has the Boosted Gear and his body is made from Great Red's flesh. Kuroka's old master was experimenting to get more power, which means he may have been weak. Theirs also a mutation piece to consider.

Consider this: Xenovia was prepared to kill an innocent-looking girl like Asia just because she was a Devil, but the two of them became best friends later on. Who's to say that something like that can't happen to Jeanne.

And if you want to talk about young, just look at Ile and Nel from Riser's Peerage, I think they're actually younger than Kunou.