King Neptune

Neptune is an enormous, muscular coelacanth merman whose face bears a reddened nose and small eyes beneath a thick mane of curly orange hair and a beard, despite his seventy years. Body hair covers both the chest and the arms, which carry matching black tattoos shaped like spirals with wavy flourishes. He goes bare-chested and is crowned with a jeweled gold piece resembling a tulip, with a gold bracelet around either wrist and a richly decorated gold trident in hand.

For Otohime's funeral he donned a large suit, and upon reaching the Red Port ahead of the Levely he put on a dark coat.

Blunt and loud, Neptune often shouts at random, including bellowing his own name, after which his whale answers with a cry of "Hoe." He is easygoing and scatterbrained, frequently scolded by his ministers for wandering off, and tends to garble names, calling Zoro "Zori." When circumstances demand it, however, he turns serious, as when he moved to detain the Straw Hats over Madam Shyarly's grim prophecy, intending caution rather than punishment. In his youth he killed for vengeance, but in his later years he became deeply merciful.

He adores his daughter Shirahoshi and frets endlessly over her safety, even willing to entrust her to strangers rather than leave her in Vander Decken IX's grasp. He grasps the gravity of the Void Century, the Poneglyphs, and the fact that Shirahoshi is the reincarnation of the Ancient Weapon Poseidon. Having once been a soldier himself, he came to believe the cycle of hatred between humans and merfolk could only be broken over time, and he refused to repay his wife's murder with revenge because she would not have wished it. Like many in the series, he carries a distinctive laugh.

In his early years Neptune fought as a soldier, avenging fallen comrades while killing and capturing many humans. He befriended Whitebeard in their primes, and shortly after taking the throne he showed the visiting Roger Pirates the Poneglyphs housed in the Sea Forest. He also shared drinks and laughter with King Harald of Elbaph. Together with his late wife Otohime he raised four children. While Otohime campaigned for reconciliation with humans, Neptune backed her efforts, but she was assassinated in public by Hody Jones, who framed a human pirate for the crime. Torn between grief and duty, Neptune locked himself away yet ultimately honored Otohime's wish to forgo vengeance.

During the Fish-Man Island Arc he welcomed the Straw Hats for rescuing Shirahoshi's pet Megalo, but Shyarly's prophecy sparked conflict, and Zoro effortlessly turned aside his trident before he and his guards were chained up. When Hody launched his coup, Neptune sided with the pirates, was captured alongside Zoro, Usopp, and Brook, and was paraded toward execution at Gyoncorde Plaza. Hody publicly confessed to murdering Otohime, devastating the king, but Luffy intervened in time. Once the rebel crew was beaten, Neptune freed the enslaved humans, sentenced the surviving rebels to penal labor, cleared the Straw Hats of all charges, and later confided the legend of Joy Boy and Noah to Nico Robin.

After word of Luffy's deeds at Totto Land and of Jinbe joining his crew, Neptune resolved to place his realm beneath the banner of the Straw Hats should it ever lose Big Mom's shelter, then departed for the Levely. There he met Monkey D. Garp, watched Shirahoshi marvel at the open sky, and very nearly attacked Charlos and CP0 to save her before Mjosgard intervened. In the Final Saga, he listened with his family to Vegapunk's broadcast about the rising sea and dismissed its warning as absurd.