@Veshv I agree that person is Hachina, and considering Midara is the one who decided the game, I honestly believe that no other referee would still know that the leader is still on the island.
My guess is since we already saw the other police grandma on the island, the other guy should be here too, and the outline matches his looks. Of course this assumption is purely based on the fact that the two new referees haven't seen the leader, but considering they were recruited during the tower game, and the leader escaped around that time, that probability is high.