Saitama Group

The Saitama Group is a group of heroes that have affiliated with or hang out with Saitama. The group comprises of S-Class heroes, Saitama, and a few other heroes that often hang out with Saitama.

Overview
Although not an official organization, these group of heroes are those who have affiliated themselves with Saitama or usually hang out with him. These heroes were originally the ones who responded to Saitama's call. Saitama calls these people his acquaintances, but they've seemed to grown on him. As said by Fubuki, the strong seem to be attracted to Saitama, so she sometimes affiliates herself with him as well. They are usually invited to Saitama's apartment cookouts or to play video games (usually just King). Saitama and Genos have periodically been invited to Bang's dojo and King has often invited Saitama to come to his apartment to play video games.

History
Fubuki challenged Saitama and his group to a competition where the losing team must obey the winner. The heroes who responded to Saitama's call were Genos, King, and Bang, much to the bewilderment of the Blizzard Group. The term "Saitama Group" was coined by Fubuki herself. Originally, the group consisted of these four members, but Fubuki has recently been affiliating herself with Saitama due to his attraction of strong members. In the webcomic, Overgrown Rover and Black Sperm followed Saitama home and are now affiliated with him. Although, they are more seen as pests and Saitama doesn't want much to do with them.

House of Evolution Arc
Before joining the Hero Association, Genos traveled from town to town to defeat monsters and evil organizations in order to try and find the evil cyborg that killed his family. At Z-City, Genos is facing off against the House of Evolution's Mosquito Girl and eventually starts getting beaten down. Genos is about to self destruct until Saitama interferes and slaps Mosquito Girl, killing her. Genos, greatly surprised by this, asks Saitama his name and wishes to be disciple. Genos will later appear at Saitama's house a week later and thus begin the partnership between the two.

Monster Association Arc
Bang and Bomb come to Genos's aid as he is fighting Garou. The two martial artists continue to beat down Garou with Genos watching in awe. Garou eventually powers up in a fit of fury and rage, but they are interrupted by monsters from the Monster Association. They manage to kill off the monsters, but Phoenix Man saves Garou and calls in Elder Centipede. Despite the efforts of the two powerful martial artists and Genos, they are unable to defeat Elder Centipede. They are forced to run away in order to save the heroes, but eventually face a dilemma of whether to try and fight the centipede once again or lead it into the city at the cost of many lives. Eventually King arrives at the scene, announcing to Elder Centipede that Blast is with him so that the monster can exact revenge on the #1 S-Class hero. As the monster charges at King, Saitama comes out behind King and kills the monster with a serious punch.

The Saitama Group regroups at Saitama's apartment after the fight with Garou, Elder Centipede, and some of the monsters from the Monster Association. Fubuki enters and sees that King and Saitama are playing video games, Bang and Bomb are recovering, and Genos is repairing himself. She tells them about the growing danger of the Monster Association and needs for them to act, but Genos states that they just fought a battle. It is revealed here that Genos, Bang, and King's communicators with the Hero Association have been destroyed from their fight with the monsters. While Bang, King, Bomb, and Genos stay back to recover (although King says he just has other things to do), Saitama heads out to hunt for Garou and buy some cabbage. Fubuki thinks to herself that getting the Saitama group to join her group is harder than she thought.

Numbers
After being challenged by Fubuki, Saitama arrived with his group which consisted of S-Class heroes Genos, King, and Bang. However, this was all according to plan by Fubuki, and she made them sign a contract without them even reading it. Instead of a head on physical battle, Fubuki insisted on a video game competition. Bang, Genos, and Saitama are quickly taken out of the competition. King was able to single-handedly take out her thirty gamers. Since Saitama's group won the competition, the Blizzard Group would have to obey them.

Trivia

 * The heroes within the group acknowledge Saitama's true strength and are the few individuals who truly see him for who he is despite his outward appearance.
 * The group itself is technically the strongest group within the series as it contains Saitama himself along with the multitudes of S class heroes, all of which are incredibly strong in some shape or form.
 * The group was founded naturally, without any initiation or recommendations to establish such group and acts much more akin to normal human side of the otherwise extraordinary individuals.
 * So far Saitama Group is the only group that owns a group under its command, notably Blizzard Group that lost through video game bet.