Shirahoshi is the mermaid princess of the Ryugu Kingdom in One Piece and one of the ancient weapons, Poseidon. She is the youngest daughter of King Neptune and Queen Otohime, and is known for her enormous size, gentle nature, and emotional sensitivity. Despite her fearful personality, she plays a crucial role in the series' larger world-building and political conflicts, especially involving Fish-Man Island, the Sea Kings, and the balance of power among the world’s major forces.