The Teacher is NOT a Troll - Tilly Catch

Dai and Bear are ordinary kids.

Well, not totally ordinary. There is the fact that they fight with swords and are training to be knights. And their mother is a dragon-wrangler who works for the fire department. And their dad works for the city council, making sure no one builds a shed over a goblin warren. And they regularly fight monsters.

Perhaps they're not that ordinary.

Oh, and they're almost certain their headmaster is a troll.

There's still some doubt about the teacher though...