He's forced to mature rapidly, but he's definitely a self-centered brat for the first few chapters. He's better after the ship.
Yeah, he definitely gets better once he realizes he has... well, nothing except his Kingsguards. He quickly learns he isn't the center of the universe, in all the routes. He's the most bratty (for longer) with Ramos, I think so the rhino can tell him off.
To me, he's most quickly humbled with Koshiro.