Hibou's feed

I'm looking for a story, I wasn't reading this for the plot so it might not really fit

It's in color, childish style.
We have a knight who lived a looong time, probably because he collected a stone/orb or was cursed after defeating a demon.
A prince (or a magicien ?) with long white hair is looking for him to solve some problem (is he cursed?), idk if they succeeded in their quest lmao

If it helps I know they fucked on a horse