In an endless sea of sand drifts the Mud Whale, a floating island city of clay and magic. In its chambers a small community clings to survival, cut off from its own history by the shadows of the past.

Chakuro and the other Marked children have freed the Unmarked from the Amonlogian dungeon, but their rescue mission is far from over. The people of the Mud Whale still need to get back to their island home, and the path to safety is blocked by imperial soldiers. Even worse, Orca is determined to secure Ouni in order to carry out his diabolical plans!