He's about to get kicked out of the party and join an official clan. Not out of spite or anything, but remember he's technically not the leader of the party. If the leader has no real plans in following his plans, then one of the only compromise is for MC to leave. At least, that's what I'm guessing that last panel implies, I would guess. I would doubt MC would be able to make a clan all by himself anyways, if his thought progression was to go from "party" to "clan".