Saitama/Relationships

At the start of the series, Saitama spent most of his time alone being a hero, but after meeting Genos and joining the Hero Association, he gradually gained numerous acquaintances and rivals.

Genos
Saitama met Genos after the latter was defeated by a monster and tried to self-destruct, but was saved by Saitama. After being saved Genos asked to be Saitama's disciple, to which Saitama nonchalantly accepts, thinking he wasn't serious. Though Saitama was annoyed by the thought of having a student, he gradually warmed up to Genos, even becoming angry after hearing he was defeated by the Sea King.

Bang
Saitama met Bang when the giant meteor was heading towards Z-City. Bang was amazed by Saitama's strength and tried numerous times to recruit him in his dojo, but to Saitama's disinterest. Bang will occasionally invite him on cookouts and vice versa.

King
King (unintentionally) took credit for killing five mysterious beings that were actually killed by Saitama. This caused King to have the fame and 'fortune' as a S-classed Hero. Saitama discovered King's true personality and the secret to his success. Saitama wasn't upset or angry at King's secret and the two would become friends. Saitama would go to King's house to play video games and become frustrated at losing to King.

Flashy Flash
While the two are particularly close like Bang he has tried to recruit Saitama after witnessing his skills personally, only to be turned down by Saitama.

Fubuki
Fubuki, after her first encounter with Saitama, was sometimes seen along with King and Genos hanging out in Saitama’s abode. She is apparently obsessed in making Saitama join the Blizzard Group. Her latest attempt was to beat Saitama in a video game competition, which failed due to King’s assistance. Saitama himself declared, that he doesn't view Fubuki as a friend, but as an "acquaintance".

Tatsumaki
At their first encounter, Tatsumaki didn't think much of Saitama due to his ranking and would insult him. She was even insulted from him ignoring her. Saitama mistook Tatsumaki for a child due to her small stature, and found her to be annoying. 'The following section contains Webcomic spoilers. You have been warned manga-only readers.'

Their next encounter would be when they 'fought' in the Psychic Sisters Arc., where Tatsumaki finds out how powerful Saitama really is. Saitama displayed concern and interest toward Tatsumaki, as he ran after her to see if she would be alright flying home with her injuries and was interested in why Tatsumaki pushes everyone away. However Tatsumaki simply yelled at him, causing him to be even more irritated at her behavior. Tatsumaki came close to revealing her past and Blast to Saitama before deciding not to. In an audio book it is revealed the two actually met in a haunted house at a festival Saitama worked at. Saitama thought Tatsumaki was a lost little kid and Tatsumaki called him a balding samurai and thought he was a ghost when her powers didn't work on him.

Mumen Rider
Saitama and Mumen Rider share a mutual respect toward each another.

Saitama respects and acknowledges Mumen Rider's ability to continuously do the daily quotas of the C-Class heroes, something Saitama found to be a difficult job. He also compliments Mumen Rider for putting up a nice fight against the Sea King.

Mumen Rider is one of the few who knows of Saitama's true strength and treats him respectfully as a fellow hero. He sent Saitama a thank you letter and offered to pay him dinner, where he thanked Saitama personally, further showing Mumen Rider's humble and respectful nature.

In an extra chapter it is revealed that he and Saitama were once schoolmates but neither are aware of this fact.

Speed-o'-Sound Sonic
Speed-o'-Sound Sonic views Saitama as his eternal rival and vows to defeat him. Saitama views their one-sided rivalry relationship in a nonchalant manner. He doesn't mind Sonic's persistence and their continuous 'battles', even goes as far to encourage Sonic to do his best. However, he would grow irritated if Sonic starts to bother him during important activities or causing a havoc around others.

According to Genos, Sonic is one of the few people who recognizes Saitama's true strength. This recognition is what caused Sonic to stop working and continue training in order to surpass Saitama. This recognition and dedication, as well as declaring Saitama a rival and admitting defeat at his hands, indicates (in his own way) a form of respect that Sonic has for Saitama.

Dr. Genus
After witnessing destroying several of his creations Genus began to study Saitama. He theorized at some point during his training Saitama broke through a limiter that humans have but the price was his hair and emotions.

Boros
Saitama sympathizes with Boros for not finding an opponent worthy of his power. While Boros admits Saitama is his better Saitama has respect for Boros and calls him the strongest opponent he has ever faced.

Agoni
While the two have never met Saitama saved his grandson from Crabrante, which is one of the reasons Agoni founded the Hero Association that Saitama would later join.

Garou
'The following section contains Webcomic spoilers. You have been warned manga-only readers.'

Garou displays hatred toward Saitama during their fight, seeing Saitama as the collective unfairness of the world, add that Saitama is a hero, Saitama represented everything that Garou hated and was fighting against. Saitama is responsible for defeating Garou both physically and mentally, realizing that Garou wanted to be a hero instead of a villain.

Saitama showed mercy towards Garou, refusing to kill him and acknowledging his flaws.