Shirahoshi is a giant mermaid, often called the "Mermaid Princess," in the One Piece series, introduced during the Fish-Man Island Arc. Shirahoshi is the youngest child and only daughter of King Neptune and Queen Otohime. She is the princess of the Ryugu Kingdom, located on Fish-Man Island.

Appearance and Personality

Credit: Heroes Wiki 

Shirahoshi is a giant-sized mermaid with long, flowing pink hair and large, expressive blue eyes. Her mermaid tail is adorned with pale pink and gold scales, adding to her ethereal beauty. She wears a shell bra and a fish-scale patterned top and often accessorizes with a crown-like tiara and other royal adornments.

Shirahoshi is sweet, gentle, and kind-hearted, often going to help others despite her fears and insecurities. However, she is also highly sheltered and emotionally sensitive. Despite her initial timidity, Shirahoshi shows great courage when it matters most. She cares deeply for her family, her people, and the friends she makes, notably the Straw Hat Pirates.

Powers and Abilities

Credits: CBR 

• Poseidon: Shirahoshi is the current incarnation of Poseidon, an ancient weapon that can communicate with and control Sea Kings. These massive sea creatures possess incredible power and can cause significant destruction if commanded. This ability makes Shirahoshi one of the most powerful beings in the world, though she initially struggles with controlling it due to her emotional nature.

• Royal Authority: As the princess of the Ryugu Kingdom, Shirahoshi has significant influence and authority on Fish-Man Island. Her decisions and actions directly impact the island's inhabitants and its relationship with the surface world.

• Physical Strength: While not a fighter, Shirahoshi possesses the natural physical strength of a giant mermaid, which is considerable given her size. However, she rarely uses her strength in combat, preferring peaceful solutions.

Trivia

• Shirahoshi’s character design and role as a princess with extraordinary power recall classic fairy tale archetypes, such as "The Little Mermaid."

• Despite her size and the fearsome power she possesses as Poseidon, Shirahoshi is one of the most innocent and gentle characters in the series.

• Shirahoshi’s size often leads to humorous interactions with more minor characters, particularly Luffy, who quickly befriends her despite their vast size difference.

• She shares a close bond with her Neptune brothers, who are highly protective of her due to the threats she has faced throughout her life.