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Fish of Darkness (ヤミ金魚, Yami Kingyo) is a Mysterious Being and the head of Niya Niya Loans.


Fish of Darkness as human

As a human, he was light-skinned with light brown, combed back hair, short facial hair, and wore a dark purple suit with a light purple, almost white shirt underneath with frilled sleeves. He also wore two white scarf ties around his neck, multiple rings, and large circular sunglasses.

As a Mysterious Being, he becomes a pink, anthropomorphic fish wearing black BDSM equipment.


He likes Cinnamon Rolls.

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Road to Hero[]

His transformation to a Mysterious Being

As a human he had an impulsive desire inside him to buy out all the stores in Z-City, through his criminal organization that was based in Saitama's old apartment complex. After Saitama figured out their base, he beat up all his lackeys and was informed that Saitama was heading to confront him. After Saitama angered him, he triggered his transformation into a Mysterious Being called Fish of Darkness. After a brief battle, he lost against Saitama and was handed over to the police for a reward.

Abilities and Powers[]

Fish of Darkness is a fairly powerful being. He was strong enough to give Saitama some trouble, albeit this was still while he was in his early stage of training, and he was quickly defeated after Saitama became pumped up for the reward money.

Physical Abilities[]

Enhanced Speed: Fish of Darkness is fairly fast. He is able to attack with his whip in rapid succession.

Egg (Ballgag) Spit: Fish of Darkness demonstrated the ability to shoot out eggs (ballgags) from his mouth.


Whip: Fish of Darkness uses a whip. He is fairly skilled with it as he was able to give Saitama a hard time, but it should be noted that Saitama was still fairly weak at this time.


  • Fish of Darkness is the first Mysterious Being whose transformation process was shown on screen, although the "transformation" process was quite different from other transformations shown later in the series.
  • When he saw Fish of Darkness take on his new risqué outfit and appearance, Saitama doubted that the man had actually transformed from a human into a monster like he had intended to, due to Saitama having previously watched a program on television about how organisms undergo metamorphosis. Instead, Saitama hypothesizes that, rather than being a monsterized human, Fish of Darkness was merely a weirdo who had become an even weirder weirdo, thereby becoming a pervert. It is unknown whether there is any truth to Saitama's conjecture.


Mysterious Beings
Dragon (or higher) Boros Orochi *
Demon 170,000-Year-Old Cicada Larva 170,000-Year-Old Cicada Adult Armored GorillaAwakened Cockroach Baquma Beast King Bruinado Bug God Building Booper Deep Sea King Demonic Fan Devil Long Hair *Do-S *Eyesight Face Ripper Fist Fight Djinn Free Hugger G4 G5 Game-Berus Giant Crow Grizzly Nyah Hundred-Eyes Octopus Jumping Spider Macho Daikon Mosquito Girl Rafflesidon Rhino Wrestler Royal Ripper Scaledon Senior Centipede Showerhead Sky King Subterranean King Super Mouse Surprise-Attack Plum The Great Food Tub The Three Crows Unihorn Vampire (Pureblood) 
Wolf Himawari Hotdog Messenger of the Seafolk Piggy Bancon Tongue Stretcher
Less than Wolf
Unknown Alien Seer *Ancient King Angry Grandpa Autumn Phantom Red Golden-ringed Dragonfly *Benpatsu *Choze DarkDark Matter Gunner Eagle Enamel Evil Eggs Evil Eye Evil Natural Water *Falcon Fish of DarknessGale Giant Salamander Gigakigan Goddess Glasses Gyoffrey Hamukichi *Haragiri Hawk Hellfire Junior Centipede Kite Lord Great White ManakoMen's Esthetician Man *Platinum Sperm Rosie Raptora *RepteraSage Centipede Suppon Sword Devil Executioner Venus Mantrap Volten *