Unless Sun loses to Kukui, which I doubt would ever happen, especially in the first round, this is going to be Sun versus Gladion. As far as we know, Moon doesn't have any battle experience. Being pit against Gladion pretty much decides her fate. They'll likely use the battle with Gladion to establish some sort of relationship between Moon and Gladion in the semi finals, and a relationship between Sun and Gladion in the finals.
As for who will win, the only way Sun can stay relevant is if he's forced to travel. Otherwise, he wouldn't give a shit about anything. That, or the battle will be called off for some reason. I'm leaning more towards the second option, personally. Having Sun beat Null so early is not going to be realistic. That said, he did fight the Tapu, and for some reason, the Tapu did attack him. He could be stronger than I think.
Now for who's the protagonist, it seems both. A Tapu event in this chapter points toward Moon, but Sun got the Pokedex, Z-crystal, has the Pager and is from Kanto. I imagine that this event was given to Moon to establish some connection between her and Lillie. After all, Sun probably already is familiar with her, so no point in giving this event to Sun, other than to give him the Z-crystal, which he got anyway.
Sun was a lot less punchable in this chapter, so if he keeps this up, I might not hate him. Not getting my hopes up though. Unless Kusaka changes something big, I doubt I'd care about him overall. I still don't give a shit about why he wants money.
Moon is still just reacting to everything, not doing much herself. I'm still disappointed she doesn't have a cute and bubbly personality. Her official design had a huge smile on her face, and I can't even imagine her manga counterpart pulling that off. Yes, I know, different medium so different personality and it's my fault for expecting that, but still a bit disappointing nonetheless. Hoping to see more of her, though. Her being the most normal person around is a plus.
