So I'm just about done with a rewrite of my first YA fantasy. I have a trilogy outlined and planned, and this first one lent itself well to the first person as it's a relatively simple hero's arc as an introduction to the world.

There's a small group of characters that naturally see some character building from direct conversations and interaction with the MC in my draft.

As I think through the second novel, a major character I'd like to develop is at odds with the MC, so development through conversation may not be practical as they might largely be in different parts of the world.

Any tips on how to develop a secondary character like that outside of direct interaction?