Princess Shirahoshi, also known as the Mermaid Princess, is a giant smelt-whiting mermaid and the youngest of King Neptune's children. She resides in Ryugu Palace, located in the underwater Fish-Man Island. Shirahoshi is a pivotal character in the 'One Piece' series as she is revealed to be the current incarnation of the Ancient Weapon Poseidon, capable of communicating with and commanding Sea Kings. Despite her immense power, Shirahoshi is gentle, kind-hearted, and somewhat naive, having been sheltered for much of her life.