Fish-Man Island

Biodata

Feature	Information
Name	Fish-Man Island
Original Name	鱼人岛
Type	Neutral Character (AI)
Affiliation	Ryugu Kingdom
Status	Active; sovereign deep-sea kingdom ruled by King Nereus
First Appearance	Chapter 48

Overview

Fish-Man Island is a kingdom located roughly 10,000 meters beneath the sea, positioned within the cavern beneath the Red Line. It is a compulsory transit point for most pirate crews traveling from Paradise to the New World because of the region's magnetic conditions. 49 50 85

The island is enclosed by a colossal bubble and supported against Eve, the Sunlight Tree, whose light reaches the deep sea and illuminates the kingdom. 49 83 Its population is primarily composed of Fish-Men and merfolk, though the Ryugu Kingdom also recognizes citizens of other races within its territories. 262

Geography and Environment

• Deep-sea location — Situated in the Red Line's underwater cavern, on the route between Paradise and the New World. 50 85
• Bubble enclosure — A massive bubble membrane surrounds the island, allowing air-breathing visitors to enter while maintaining the underwater environment outside. 49
• Eve, the Sunlight Tree — A giant tree against which the island is suspended; it channels sunlight to Fish-Man Island. 49 83
• Coral Hill — A populated area containing lodging and commercial facilities. 72
• Sea Forest — Receives wreckage from pirate ships destroyed near the island. 338
• Fish-Man District — Originally an orphanage and later a dim, neglected slum outside the island's main bubble. Its residents were relocated under Nereus, while the former district became a training ground. 51 176
• Ryugu Palace — The royal palace and a major governmental and military site; its former grand hall was converted into a training ground. 74 83

Population and Races

Fish-Man Island is home to Fish-Men and merfolk, whose aquatic physiology gives them a decisive advantage beneath the sea. Fish-Men are naturally capable of breathing underwater and are several times stronger in aquatic combat than on land. 3

Group	Known traits
Fish-Men	Possess average arm strength ten times that of humans; many inherit species-specific traits such as camouflage, tooth regeneration, corrosive secretions, or flight. 14 78
Merfolk	Generally faster swimmers than Fish-Men; female merfolk can split their tails into legs after age thirty, while male merfolk retain fish tails. 3 84
Flying Fish-Men and merfolk	A rare group capable of sustained aerial travel using their large flying-fish traits; 209 were identified in the national census. 78 124
Non-aquatic residents	The kingdom's territories include citizens who are neither Fish-Men nor merfolk, particularly in Delta Island, Sabaody, and parts of the North Blue. 262

Government and Administration

Ryugu Kingdom

Fish-Man Island became the Ryugu Kingdom after Nereus overthrew the former royal family and declared himself king. He presented the change as the end of the island's era of insecurity and misfortune. 77 78

• King: Nereus. 78
• Princesses: Nanamo and Chloe are identified as daughters of Nereus. 174 338
• Former royal family: Removed from power during Nereus's takeover. 74 77
• National census: Nereus ordered a census of citizens' fish species and innate abilities, prioritizing identification of potential Flying Fish units. 78
• International status: The kingdom became an official World Government member nation and obtained agreements prohibiting Fish-Man and mermaid slavery. 135 151
• External agreements: Several nations signed documents promising equal treatment and settlement rights for Fish-Men and merfolk. 160

Security and Entry Controls

Ships entering Fish-Man Island lose their exterior coating when it is absorbed by the island's surrounding bubbles. Leaving requires recoating by local Fish-Men or merfolk craftsmen, allowing the kingdom to control departures and prevent kidnappers from escaping. 78

• Entry requires inspection and, later, a permit for ship coating. 78 181
• Clear signage and illustrated rules are maintained at the Sabaody office for incoming travelers. 252
• Pirates pay a transit toll of 100,000 Beli per person. 84
• Travelers can purchase New World Log Poses and other supplies unavailable elsewhere. 84 345
• Unauthorized ships are intercepted or sunk by patrols. 147 338
• A sea prohibition order temporarily closed the island to all non-citizens. 146

Military

Neptune Army

The Neptune Army is the Ryugu Kingdom's military force. Under Nereus, it was reorganized around the island's underwater advantages, citizen abilities, sea beasts, and elite combat units. 78 82

• Patrols protect the island's perimeter and enforce transit regulations. 84 338
• Recruits are assessed through Conqueror's Haki and tasked with subduing Fighting Fish to prove their suitability. 82
• Sea beasts are employed to destroy ship coatings and disable hostile vessels. 84
• Military training incorporates physical conditioning, specialized diets, Fish-Man Karate, and practical combat. 127 197

First Legion

The First Legion was formed to train the future Neptune Army.

• Commanders: Sebastian and Fisher Tiger. 83
• Recruitment method: Candidates earn recognition by subduing Fighting Fish rather than merely killing them. 82 83
• Training base: Ryugu Palace's former grand hall. 83

Royal Guard

Following the national census, Nereus selected 57 eligible Flying Fish-Men and merfolk for a military draft and Royal Guard training program. 124 127

Unit	Personnel	Purpose
Royal Guard	57 recruits	Elite defense force drawn from Flying Fish-Men and merfolk of suitable age. 124
Flying Fish Army	Not specified	Aerial unit used to train recruits such as Alber. 129
Scout force	Led by Rachel	Perimeter reconnaissance, sea-beast patrols, and underwater interception. 84
Stealth company	Not specified	Uses camouflage and mimicry traits for covert underwater operations. 194 197

Economy

Fish-Man Island's location and underwater capabilities make it a major trade and logistics center.

• Transit trade — Merchants exchange surface-world goods for deep-sea products, including pearls, coral, and rare fish. 50
• Transit tolls — Fees imposed on pirates and other passersby provide substantial income with low operational cost. 84 135
• Deep-sea salvage — The Fish-Man Pirates' primary early revenue source was recovering treasure from sunken ships and ancient ruins. 53
• Coating services — The kingdom controls essential ship-coating permits and approved coating services through Fish-Men and merfolk artisans. 78 125 181
• Security and escorts — Fish-Man Island offers protected shipping routes, insurance, and maritime security to external nations and businesses. 160 238
• Construction and infrastructure — Citizens with terrain-related abilities assist in excavation, canals, foundations, and other large projects. 239
• Research — Wobigon's work includes Sun Tree Eve cultivation and strengthening Red Yarukiman resin. 53

Infrastructure and Development

Following Nereus's accession, Fish-Man Island began rapid domestic development.

• New bubble zones were created for schools and infrastructure. 83
• The Fish-Man District's displaced residents were moved into more suitable housing. 176
• New care facilities were established for abandoned children and returning overseas residents. 176
• The kingdom expanded commercial operations to Sabaody Archipelago and Water 7. 125 306
• Fish-Man Island supplied timber to shipbuilders and became a commercial lifeline for businesses in Sabaody. 238
• The island's residents experienced greater safety and stability despite escalating piracy in the outside world. 123 228

External Territories and Influence

Sabaody Archipelago

Fish-Man Island obtained the Lawless Area of the Sabaody Archipelago through an agreement with the World Government. 119 123

• Babel established a Ryugu Kingdom overseas office and occupied a former Marine station. 125
• The kingdom protects cooperating coating artisans in return for servicing only approved ships. 125
• Although the Navy still considers it lawless, Fish-Man Island's management made Sabaody one of the safest nearby locations. 238
• Sabaody serves as a training ground for Fish-Man Island's younger generation. 123

Delta Island

Delta Island is a settlement territory associated with Fish-Man Island. It hosts the annual Day of Rebirth, commemorating the freedom and new lives of those first settled there by Nereus. 112

Other Operations

• North Blue — Fish-Man Island maintains influence through figures such as Fisher Tiger and later personnel deployments. 235 306
• Water 7 — The kingdom acquired property and recruited staff as commerce revived around the Sea Train. 306
• East Blue — Arlong's Ryugu Park operates successfully there. 306

History

Before Nereus's Rule

Fish-Man Island's former rulers failed to adequately protect the population from pirates and slave-catching crews. The Fish-Man District deteriorated from an orphanage into a lawless slum, while powerful Fish-Men and merfolk often pursued lives abroad rather than defend their homeland. 26 51 176

The island's strategic route made it valuable to merchants, pirates, smugglers, and traffickers. Its prior weakness reduced the risks faced by slave traders and left residents vulnerable. 50 51

Nereus's Takeover

Nereus arrived at Fish-Man Island, confronted smugglers, reconnected with the Fish-Man District, and began gathering local fighters such as Fisher Tiger. 51 52 He subsequently entered Ryugu Palace, informed King Pontus of his intention to overthrow the royal family, and learned that Poseidon could be reborn as a mermaid princess on the island. 74

Nereus publicly declared himself the new king, promising to replace the island's history of darkness with a secure and powerful nation. 77 78

Consolidation

After taking power, Nereus reorganized the military, conducted a nationwide census, established patrols, recruited Fighting Fish partners, built new infrastructure, and imposed transit taxes. 78 82 83 84 The kingdom's deterrence sharply reduced pirate activity through the deep-sea route. 72

International Recognition

Fish-Man Island entered agreements with the World Government, including a ban on Fish-Man and mermaid slavery. 151 It also received authority over Sabaody's Lawless Area, allowing the Ryugu Kingdom to develop an overseas office, regulate coating services, and expand its commercial reach. 119 125

Later Era

Fish-Man Island remained insulated from the worsening pirate crisis after Roger's execution, with pirate wreckage and aggressive patrols discouraging incursions. 228 338 Its reputation became strong enough that even major pirate crews were expected to obey local regulations. 356

Notable Residents and Personnel

• Nereus — King of the Ryugu Kingdom; led the overthrow of the former royal family and transformed the island's military, economy, and external relations. 74 78
• Nanamo — Nereus's daughter and a princess; participated in recruitment and island affairs. 82 85
• Chloe — Nereus's hybrid Fish-Man/Lunarian daughter; later assists with entrance security. 174 338
• Sebastian — Fish-Man officer, First Legion leader, and specialist in camouflage-based operations. 83 194
• Fisher Tiger — Former Fish-Man District boss and First Legion leader; became one of the early figures trained under Nereus. 51 83
• Sunbell — Fish-Man commander involved in the island's defense and later a school instructor. 72 194
• Rachel — Electric Ray Mermaid and scout captain responsible for perimeter patrols. 84
• Babel — Ryugu Kingdom operative stationed at Sabaody Archipelago. 125
• Wobigon — Scientist and Nereus confidant researching ancient technology, botany, Sun Tree Eve, and Red Yarukiman resin. 53
• Tom — Fish-Man shipwright with ties to the kingdom; assists Nereus with ship-destruction techniques and Pluton-related materials. 127
• Arlong — Later identified as king of Fish-Man Island and operator of Ryugu Park. 301 306

Trivia

• Fish-Man Island's waters are sufficiently difficult to navigate that a local guide can be valuable even for pirate crews descending in coated ships. 345
• The kingdom's Fish-Man Pirates are treated as a prestigious historical institution; their emblem is used as a symbol of honor by later Ryugu Kingdom personnel. 299 338
• Fish-Man Island's geography makes it hard both to enter and to leave, giving its government unusual control over ship traffic. 78
• Its deep-sea position is also a natural military advantage: Fish-Men and merfolk can travel faster and more covertly than ships underwater. 194