Bonney has been waiting for a letter from her father Kuma who promised to write to her. But with no letters in sight, she turns nine and one day realizes her disease is cured. She then decides to go out to sea to search for her father.

The present day on Egghead, Bonney is caught in St. Saturn's grasp, knowing he is responsible for her father's transformation into a cyborg. However, Saturn reveals an even more shocking truth that throws Bonney into despair.