[The peanut gallery seems content to let Atsuro field this question. He gives Yurick a small smile.]

It's the pact we have as summoner and demon. To become a summoner, you have to show that you have the strength to control them.

[...His eyes flicker away momentarily. Hopefully, Yurick could figure out what it meant if you failed without him spelling it out.]

Once you do, though, the demons that agree to fight for you will never back out on you or betray you. I think there's some sort of unbreakable law of the universe involved...

In other words, sucks to be me.

There are worlds where you contract with demons in the wild. Where I came from, though... [a slight pause] It was easier to purchase them.