Riku isn't planning to take any sides off the bat, mostly because for all his investigating, he doesn't want to be that deeply involved when they're still short on information. He's kind of got a policy about not meddling in other world's affairs unless/until it's a necessity, so he's been staying as neutral as possible while looking into things.

That said! He's mostly likely going to accidentally wind up siding with the humans. A lot of that will be because he's going to be looking out for the player characters and trying to make sure no harm comes to them. So whether that's jumping into the fray to protect someone or just getting in-between others/NPCs that are fighting just to minimize the collateral damage. He's been interested in the goblins' side of things, but when push comes to shove in a situation like this, his priorities come with protecting and looking out for his comrades, not really either side of the world's matters.

So if anyone winds up in a pickle and wants a giant key-wielding smartass to come to their rescue/fight alongside/etc, count me in and I'll make it happen! He can also heal people with cure spells if they have injuries up to a certain extent.