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Mysterious Beings
Monster Spread

Mysterious Beings (怪人, Kaijin), or monsters, are non-human creatures that pose a threat to society.


According to Dr. Genus, Humans can naturally become monsters from a desire to transform into something else through their bad habits, a complex, or a burst of dissatisfaction with their regular selves. These factors trigger abnormal cell reactions that prompt their transformation. Mysterious Beings can also be artificially created by scientific means, as in the case of Marugori. Non-human life can also be transformed into Mysterious Beings through factors such as pollutants, environmental changes, and genetic engineering. Some Mysterious Beings belong to non-human races and are considered natural adversaries of mankind. For example, Pureblood came from a bloodline of ancient vampires; Boros was born an alien.

The biological mechanisms of some monsters are similar to humans; their metabolic processes require oxygen intake and carbon dioxide waste emission.[1] Other monsters operate by the use of inexplicable methods. For example, the only organs Evil Natural Water possesses are its eyes and heart, so how it controls its liquid body is a mystery.

Generally, when a human transforms into a monster through excessive compulsive behavior, their resultant transformation draws influence from their obsession. For example, Crablante overate crab and became a crab monster; Devil Long Hair's obsession with hair gave his monsterized form the ability to manipulate his hair. On the other hand, transformation via monster cell ingestion amplifies the strength and talents of the user. The drawback of this monsterification method is the loss of the ability to develop further strength.[2] According to Choze, who ate a monster cell, a drug is secreted in the brain which removes the morals of the user. Mysticism may also be a means of transformation into a monster, as in the case of Sword Devil Executioner, who sold his soul to his blade and turned into a monster.

The frequency in monster appearances has increased in the past 15 years.[3] Reasons for hostility against humans vary. Monsters like Piggy Bancon and Tongue Stretcher are simply public nuisances. Creatures like Crablante and Surprise Attack Plum attack to exact revenge. Clans of creatures like the Seafolk and the Subterranean People seek possession of the Earth's surface. Still others like Vaccine Man and Homeless Emperor aim for utter extermination of the human race.

Mysterious Beings are especially concentrated in Z-City and Q-City.[4] These monsters are the reason Agoni founded the Hero Association.[5]

The Monster Association was created to oppose the Hero Association and cause chaos on Earth. The existence of this organization is proof that monsters, despite their innate compulsiveness to act rashly, can cooperate under an organized system. Mysterious Beings also seem to be able to detect the distinctive auras of other monsters as large numbers of monsters headed to Z-City to join the Monster Association.[6]

Some Mysterious Beings, or parts of their body, can be edible for humans as seen when Saitama ripped off all of Kombu Infinity's leaves to cook his kombu stock and suffered no ill effects.[7] This is also seen when the Hero Hunter, Garou, eats the arm of a Mysterious Being he had just killed and suffered no ill effects.[8]

List of known Mysterious Beings by Disaster LevelEdit

*There are also numerous unnamed monsters.

List of known Mysterious Beings by Disaster Level (Webcomic)Edit

Types of Mysterious BeingsEdit

There are numerous types of monsters, and some monsters belong to multiple categories.

Natural Type: Sentient races that have been dormant and/or living in seclusion from the humans.

  • Extraterrestrials (Aliens): Sentient beings alien from Earth. All members of the Dark Matter Thieves belong to this type, and along with the unnamed Alien Seer, are the only known aliens so far.
    • Boros' Species: A race of beings that developed the greatest regenerative ability in the entire universe to adapt to living on their home planet, which had harsh climates.
  • Seafolk: A race of beings that originate from the sea.
  • Skyfolk: A race of beings that originate from the sky.
  • Subterranean People: The self-proclaimed "True People of the Earth". They live under the earth's crust, but grew too numerous in numbers and planned to take over the surface.
  • Terror Lizards: Dinosaurs that have come from mountains to take the surface of the earth for themselves.
  • Vampires: Ancient bloodsucking creatures with a long history.
  • Forest Tribe: A race of beings of unknown origin that have come to revive the lost greenery with fertilizer made of human corpses.

Unusual Type: The most bizarre type are the Mysterious Beings that were normal individuals whose change happened through performing an action obsessively. Men's Esthetician Man became a Mysterious Being of this type after obsessing over makeup constantly.

  • Ugmons: Ugmons are grotesque creatures created from ugly humans.
  • Costume Monsters: A type of monster which is the result of a person combining with their "costume", they all share similar spirit to one another and thus have unity.[9][10] Phoenix Man and the hypothetical "Brave Giant Man" are part of this type, it was also implied that Watchdog Man could be one of them. Crazy Brown Bear seemed to be a costume monster as well.

Artificial Type: Normal beings or individuals which, by scientific means, gained superpowers or mutations.

  • Mutant: Mutants are creatures created through genetic modification.
  • Robot: Robots with artificial intelligence that pose a threat to humans are treated as Mysterious Beings. G4 is one such example.
  • Cyborg: Cyborgs are cybernetically enhanced living beings.

Humanoid Type:[11] Mysterious Beings who are hard to distinguish from regular humans in terms of appearance. Devil Long Hair, Do-S, Gale Wind, Hellfire Flame, Maiko Plasma, Suppon and even vampires and ugmons in general are part of this type.

Non-Sapient Type: Some Mysterious Beings are just feral beings with no higher brain function, similar to that of a wild animal.

Human Type: A human who is designated as a monster without actually becoming one or only half-way of becoming one. Garou before his transformation and Homeless Emperor are two examples. Espers such as Psykos could be considered to be this type.

Infused Type: Mysterious Beings who are the result of a human or animal consuming the uncooked flesh of a monster. For example, a human who has eaten a Monster Cell or the crows who ate the Beast King's flesh. Several have displayed the ability to switch back and forth between their human and monster forms.

Disaster LevelsEdit

Disaster Levels

Disaster level threats. Clockwise from top left: Tiger, Demon, God, Dragon

Mysterious Beings are assigned disaster levels to estimate their destructive potential. The levels are as follows (in order of increasing threat level): Wolf, Tiger, Demon, Dragon, and God. Although the disaster level system was created to estimate the threat levels of Mysterious Beings, it can also be applied to other threats, such as villains like Garou and natural disasters like the giant meteor. They give heroes and citizens an estimate of what level of danger to expect. The Monster Association also assigns disaster levels to its members.
Disaster Level Pamphlet Recreation

The Hero Association's disaster level pamphlet

Several factors are taken into consideration when determining a disaster level. These factors include aggressiveness, the difficulty of extermination, and combat prowess.[12] Disaster levels sometimes do not correctly indicate how threatening a threat is to human society and thus do not truly represent individuals' combat prowess when compared to one another. For example, Gouketsu was much stronger than Bakuzan, even though both were classified as Dragon-level threats.

Disaster levels can be incorrectly assigned. These may be due to the Mysterious Beings hiding their strength such as Withered Sprout, ignoring context-dependent factors such as suitability to the particular event or an individual defeating monsters without reporting their true level of strength. While heroes engage monsters, they sometimes must update the Hero Association on the correct threat level. While some heroes stick to attacking weaker Mysterious Beings to maintain their ranks, defeating a high disaster level monster is very influential on hero rankings. Many heroes challenge these powerfully ranked monsters to move rapidly up the hero ranks such as Stinger who rose to the top 10 of the A-Class within six months.[13]

Disaster Levels and Descriptions
Disaster Level Descriptions
God A threat endangering the survival of all humanity.
Dragon A threat endangering multiple cities.
Demon A threat endangering a whole city or its infrastructure.

Based on the official comparative scale, the average Demon threat requires:

  • 10 A-Class heroes or
  • 1 S-Class hero to defeat.
Tiger A threat endangering the lives of a great number of people.

Based on the official comparative scale, the average Tiger threat requires:

  • 5 B-Class heroes or
  • 1 A-Class hero to defeat.
Wolf Appearance of a being or a group that might pose a threat.

Based on the official comparative scale, the average Wolf threat requires:

  • 3 C-Class heroes or
  • 1 B-Class hero to defeat.
Less then Wolf No threat at all, only known being to be this level is Monster Chick Man.


  • Wolf is never used or even considered a disaster level in the anime.
    • This is most likely due to the near lack of Wolf monsters in the manga at the time.
  • God level threat is represented by a Fenghuang, which is rather ironic, as the Fenghuang is often associated with virtue and grace and has positive connotations.


  1. One-Punch Man Manga; Chapter 97
  2. One-Punch Man Manga; Chapter 92, page 5
  3. One-Punch Man Omake; 200 Yen
  4. One-Punch Man Manga; Chapter 20, page 8
  5. One-Punch Man Manga; Chapter 15, page 24
  6. One-Punch Man Manga; Chapter 80, page 14
  7. One-Punch Man Manga; Chapter 20, page 37-40
  8. One-Punch Man Manga; Chapter 90, page 43-44
  9. One-Punch Man Manga; Chapter 100
  10. One-Punch Man Manga; Chapter 101
  11. One-Punch Man Manga; Chapter 61, page 3
  12. One-Punch Man Manga; Disaster Level
  13. One-Punch Man Encyclopedia; One-Punch Man: Hero Perfection, page 32


Mysterious Beings
Unaffiliated Crablante Vaccine Man Marugori Piggy Bancon Giant Snowman Himawari Personification Of A Light Pull Cord Kombu Infinity170,000-Year-Old Cicada Larva 170,000-Year-Old Cicada Adult Demonic Fan Delorean Alien SeerThree-Eyed Ghost Surprise-Attack Plum Tongue StretcherGiant Crow Octopus Claw Man Grizzly Nyah Suppon Gigakigan Hotdog Game-Berus Autumn Phantom Red Golden-ringed DragonflyJumping Spider Scaledon Enamel Black Roast Macho Daikon Withered Sprout Twin-Headed Tsuchinoko Man-Eating Capybara Pot Bellee Kenzan Rat Pesky Clown
Native Tribes Forest Tribe (Forest King ) • Seafolk (Deep Sea King Lord Great White Messenger of the Seafolk ) • Skyfolk (Sky King Eagle Hawk Falcon Kite ) • Subterranean People (Subterranean King ) • Terror Lizard Clan ( Ancient King )
Dark Matter Thieves Boros Geryuganshoop Melzargard Groribas Dark Matter Gunner 
The Organization G4 G5 
House of Evolution Carnage Kabuto Beast King Armored GorillaKamakyuri Ground Dragon Frog Man Slugerous Mosquito Girl 
Anime-Only Mysterious Beings Super Custom YO649Z Mk. II Fish of Darkness *Pluton Men's Esthetician Man *Dirt Earthworm Japanese Giant Salamander Lord of Mountains TV Junkyard Monster Urn Eel Crazy Brown Bear 
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