User blog comment:B214/Question and Answers 2/@comment-98.26.119.147-20140125015213/@comment-1359322-20140125030225

Actually Asia has aptitude with magic not demonic powers. Maybe Asia's bilogical parents are magician or something. Not sure since it was never mentioned.

But here's a few thing about Evil PIeces that a Devil needs to consider.

First is the trait. What trait is the servant that you're going to reincarnate going to fit to. In that sense, most Devils would ignore those that show completely zero talent and trait.

Second is the cost/worth. How much is it going to cost them, when reincarnating a Devil, of course if the cost is higher than the potential of the servant is better.

Third is the potential. Some Devils will not show any strength at all in the beginning but might become stronger if trained properly. Yuuto is the best example to that, he only used 1 Knight Piece and he still reached his current level of strength.

Fourth is the balance of the team. The master can't simply reincarnate anyone with potential, it might cause trouble with teamwork or might even affect each others power.