So Imu's childish actions are reminding me of another anime.
Anyone ever read Shugo Chara? In it, the big bad of the evil company attacking people turned out to be a little boy at the head of it, put into power by his grandfather (his parents were dead) and all the old guys answered to him.
Maybe Imu was a child/teen saved by his mother (we get a lot of mother sacrifices in this story) by use of the Ope Ope no Mi, then since it killed her, Imu was raised by the elders as figurehead, who now listen to him.