King/Synopsis

History
In his childhood, King had won several video game tournaments. At some point within the past 1.5-3 years, King was attacked by the Octopus Claw Man, receiving his characteristic three scars as a result, but is saved by Saitama, who was training to be a hero at the time.

Saitama would go on to save his life five more times by destroying the monsters in his vicinity, Vaccine Man among them, but King would always, and unintentionally, get the credit since he fell into the remains of Vaccine Man’s blood on the floor by accident. The Hero Association, capitalizing on the reputation of his strength, made him an S-Class hero without having to take the hero exam and King would be known as "the strongest man on earth". This would continue and King would be paid for the deeds that he had not done.

Alien Conquerors Arc
King appears at the S-Class Hero Association meeting. During the attack of the Dark Matter Thieves, King is standing on top of the Hero Association's headquarters along with Genos, Child Emperor, Tatsumaki and Superalloy Darkshine after having crawled up from a hole that Saitama made. While Child Emperor considers how to deal with the Dark Matter Thieves' mother ship, Superalloy Darkshine takes the initiative to ask King for his opinion on the matter. King's engine activates as he simply replies that there's nothing he can do. In response to their questioning looks, he follows up with stating that the target is too far up in the sky for him to attack, and suggests that they should use the opportunity to call Metal Knight instead. Tatsumaki promptly protests by calling King pathetic for not taking initiative against the enemy, who has already laid waste to A-City, but is still heeded as the world's strongest man. Superalloy Darkshine warns Tatsumaki that King might kill her if she angers him.

King Arc
During a walk in his home city M-City, he involuntarily encounters Tongue Stretcher and his perverse assault on pedestrian women. Whilst silently deploring his status as a hero, he stands next to the mysterious being as his cover is blown off by the wind, revealing his fearsome malicious stare along with his King Engine. This merely startles Tongue Stretcher at first, but shortly startles him into despair as he is overwhelmed by the menacing aura. A bystander quickly recognizes King's identity and shouts out his name, reminding Tongue Stretcher of who he is up against. The bystanders cheer King on as the monster cowers down on his knees and begs for forgiveness. The surrounding citizens shout various positive and negative remarks at King and the monster, who is supposedly having a seizure from excessive crying, respectively. King is soon crowded by fans who shower him with questions, admiration, love confessions and the likes. Someone asks if he came from sensing a monster, but King says that he was just shopping. Someone else comments on King's face, claiming that he was pissed, but King mildly objects. He picks up his cap to brush it off and declares that he was in a hurry and needed some space. The crowd gets alarmed and fusses about giving King a path and apologizes for being intrusive. King carries on with his business and stops by a TV-game retail store to buy a dating sim called Doki Doki Sisters. Relieved to have finally bought it, King makes his way home while relishing the excitement of having a newly bought game with him. However, it doesn't take long until he hears the screams of another "monster" showing up. Behind him lands a giant robot who introduces itself as G4; a "machine god" created by The Organization. G4 remarks King's status as the world's strongest human and thus that it has come to kill him. Someone recognizes King and shouts out his name. The fleeing pedestrians stop and form a cheering crowd behind him, convinced that everything will be fine now that King is here. Questioning the robots origin, King warns it of his title as the Rank 7 S-Class hero "King; the strongest man on Earth". G4 pays no heed to his rebuttal and swings down a giant sword at King, knocking his hat off and restates that it has come to kill him. The robot follows up by informing King that this is for a battle AI performance test, to which King has no idea what it is talking about. He goes along by saying that he must go to the bathroom first in order to fight at full strength, reasoning that it couldn't get sufficient data if King was holding it in. This convinces G4 and gives King a ten-minute bathroom break. However, G4 warns that if he does not come back within that time, ten people will die each minute and that if he runs away, the town will be no more. King enters the bathroom and drops his game on the floor. His breathing quickly accelerates to hyperventilation as he realizes that his name and reputation have no effect on the robot who came to fight him. Hearing of the impending destruction, which, unbeknownst to him is actually Genos facing the robot, King attempts to formulate a plan for a moment but fails to come up with one and runs from the bathroom with his game, silently apologizing to the masses he has abandoned. Returning to his apartment, King starts up his game system to relieve himself of the stress and debates about what name to use. Saitama suggests that he use his hero name and only then does King notices him. Saitama reveals that he entered through the open window, though King notes that he lives on the 22nd floor of his complex. King attempts to frighten him off by taking advantage of his reputation as an S-Class hero, but Saitama is unfazed, merely expressing surprise at the fact that King bought a dating sim. A horrified King tries to cover it up by claiming that he was aiming to buy an action game but mistook the title for one of an action game. Saitama then suggests that they play one involving robot battles instead, believing that King ran away from the robot because he was bored. King reluctantly plays the robot game instead, inwardly fuming about Saitama's intrusive presence and his interruption of his peace. Saitama then asks him about fleeing from G4, noting that Genos is fighting in his place instead, causing King to spit out his juice in shock and his heartbeat to quicken in an attempt to find a suitable answer to Saitama's questions, unaware that Saitama believed that he had found a kindred spirit in him. Shortly after, a Demon-level Giant Crow spies Saitama's bald head and lunges right into his apartment, wrecking the area. Saitama, believing that the Giant Crow headed for King instead, suggests that King had no choice but to fight it back. Unwilling to die from Saitama provoking the bird, King shuts his eyes and shouts the truth behind his alleged heroism.

Hearing the ensuing conflict, King initially believes that Saitama was eaten by the Giant Crow, but opens his eyes and realizes that Saitama had defeated it. Saitama then realizes that King's alleged fight history and strength were all lies, noting that King had urinated in his pants from the bird's attempted attack. Saitama asks if he is okay, at which point King realizes that Saitama was the hero who saved him in his previous encounters with mysterious beings.

A tearful King apologizes for unfairly taking the credit that should have been Saitama's, but Saitama brushes it off, instead asking King whether it was fun pretending to be a hero while being scared, to which King replies that it was not, and whether King would continue or give up hero work, to which King replies that he does not have the guts to decide. Saitama replies that King just has to become stronger and tells King that he might come over to play video games with him and leaves.

The Blizzard Group Arc
King visits Saitama's place in order to retrieve his portable video game console. Saitama confessed to erasing the data, which King accepted and didn't mind, but noted that the button was broken. Fubuki was surprised with King's entrance, wondering how S-Class heroes are attracted to Saitama.

Monster Raid Arc
King is called by the Hero Association to help them protect the Association's sponsors, upon which King replies by saying he's busy defeating a monster, specifically a monster in a video game.

Super Fight Arc
While playing a video game, the power goes out and he notices the sirens.

Monster Association Arc
King meets Saitama in a deserted street and tells Saitama he was going to buy a manga, when he noticed that Saitama looked sad. King and Saitama share a deep conversation about being a hero and King gives Saitama some insightful advice to him, though he copied it from a manga. King then invites Saitama to play video games and promises to play with only two fingers, which perks the latter.

King was then spotted by Garou, who was injured during his fight with Watchdog Man. Just as Garou was about to hit King, Saitama kicked Garou into a wall, saving King.

He later plays against Saitama and defeats him, despite having a two finger handicap causing Saitama's extreme frustration for losing King too many time in video games.

When King reveals to Saitama the emergency transmitter and the request for help that involves Genos, Saitama begins to worry for his student's well-being. He and Saitama decide to go to help Genos.

He joins the other S-Class heroes in the fight against the Monster Association. At one point, it is only him against Gums, Black Sperm, Evil Natural Water and Homeless Emperor. Yet thanks to his very convincing and intimidating bluffing, he is able to make the dragon level monsters hesitate, as they wonder if King has already figured out their techniques just from looking at them. But Black Sperm remained unconvinced, and just as he was about to attack King, he was saved by Fubuki. After Tatsumaki is defeated by Black Sperm, Child Emperor tells him to beat Black Sperm. He uses his Ultimate Hellfire Wavemotion Technique, and it seems to have a large effect. This was only to be in King's head. He then flees from the scene and it was taken as a bluff technique.

Psychic Sisters Arc
He comes to Saitama's new place to welcome him there but he isn't around. He defends him saying that Metal Knight's robots self-destructed.