"Individuals from worlds with no known magic have indeed learned to use it upon being introduced to travelers from other worlds."

That's a detail he's counting on with Ken, even. If Sora can learn grand magic, surely Ken can at least learn basic level spells.

"Certain forms of magic may be inherent to specific worlds, and thus difficult or impossible to use outside of them, but learned spells can be taught and learned freely so long as one has a competent teacher."