Walking into the Fish‑Man Island section of 'One Piece' felt like being handed a whole new cast all at once — and I loved it. The most immediate and unforgettable debut is Shirahoshi, the enormous mermaid princess who is later revealed as Poseidon. That introduction alone reshaped the stakes of the series for me: an innocent character who literally holds an ancient weapon alters the whole map of grand politics in the world.
Alongside her we meet King Neptune and his three princely sons — Fukaboshi, Ryuboshi, and Manboshi — who give the Ryugu Kingdom some real royal flavor. The arc also brings in the main villain Hody Jones and his New Fish‑Man Pirates, a group that includes memorable muscle-types like Dosun and ruthless lieutenants whose resentment fuels the conflict. Vander Decken IX makes his first creepy appearance as well, staking a claim on Shirahoshi in a way that ties into larger series threads.
The arc layers in important flashback introductions too: Fisher Tiger and Queen Otohime show up in the island’s history, and their stories are crucial for understanding the racial tensions and tragic decisions that led to the present. So if you’re counting debuts, think of Shirahoshi and the royal family, Hody and his crew, Vander Decken, and the flashback figures — all characters who immediately add weight and worldbuilding. I still get chills picturing the Sea Kings and Shirahoshi together; it’s one of my favorite wild moments in the series.