They are diligent and excited.

Before they can summon their first daeva Kaede informs them of the risk of becoming one after death.

That sounds... probably cool? Compared to being dead.

Yeah he thinks it's a pretty sweet deal but who knows some people might have objected.

Okay so who wants to summon a fairy?

These greens want to!

So they can summon! Hi fairy these are students they are learning how to summon to get their license.

"What's with the hair?" asks the fairy.

"Everyone at school has green hair," says a green earnestly.

"Huh. Okay."

So: they can make a deal with the fairy, something in exchange for (usually) some service, and then the person who summoned them has to concentrate on wanting them gone for a minute.

They ask the fairy if it's okay to resummon him a few times so they can each have a turn and then the fairy can have a stack of paper books. The fairy accepts. They each have a turn and the last one gives the fairy the books.

The lessons will probably progress quite nicely, then.

Yup. It turns out handpicked greens working on a secret project integral to the future of their entire species learn faster than college kids who are dividing their time between summoning, English Lit, and beer.

Sorta expected, really. He designs a test different than the one he passed because honestly fuck gags.

The book mentions them but the greens don't really see the use unless it's a common problem for daeva to talk at inopportune times in an attempt to mess up their summoners.

It's not; he explains the reason.

Can't people just... not trade their souls?

In theory demons are just that good at convincing others to sell their souls. But also demons can't actually do that.

They will spot each other while summoning demons in case it turns out Kaede is mistaken and conventional wisdom is correct.

That is reasonable! Some demons may in fact offer to get their souls but they're not typically supernaturally persuasive about it.

Why do demons want souls?

Kaede thinks it started as a pretty common prank and then since people would only gag demons the ones who do answer are the ones who don't mind being gagged so there's some selection for being so altruistic you want to help or for being able to get what you want in spite of the gag, which is easy when the thing you want is stereotypical.

Huh.

They could also ask the demons?

They make a note of that.

And eventually they will in fact get to summon demons!

Yes! Terraformer demons!!!