Zorori and the twins are traveling on a raft at sea when they begin talking about mermaids. It is said the mermaid princess seduces sailors with her song, causing them to crash into the rocks and then dragging them to the bottom of the sea. Suddenly, a song fills the air. The mermaid's song. Zorori decides he will let the mermaid take him to the bottom of the sea, because a mermaid princess must have a castle. He decides he will take her castle as his own. It turns out the mermaid princess is just a child, and her castle is actually the AI house Duke Bururu gave Zorori: Zorori Castle!