Board Thread:Questions and Answers/@comment-22798516-20130923164947/@comment-10929317-20130925072332

if i remember correctly, it was actually kageyama that made that rule...? (according to scans or an interview or something) i always assumed he did it because otherwise the kids in shinsei inazuma japan would be crushed in the first round.... and considering soul's much stronger than keshin (keshin are the energy produced by the player forced into a physical form?? soul is their actual soul???) i doubt they'd be using them even if they were allowed to.

i'm fairly sure the aliens can use soul (i always took it as humans were one of only a few species that could) but they also seem to have other abilities too - the aliens in sandorius were ridiculously strong, after all.