Due to him saving her when she was younger, Tatsumaki highly respects Blast. Blast was the one who told Tatsumaki to not rely on others to rescue her but Tatsumaki took it too far distancing herself from everyone but her sister Fubuki and Blast himself. The two would later join the Hero Association and are the two highest ranked heroes in the association. Since Blast went missing Tatsumaki has been wondering when he will return.
Tatsumaki's younger sister and fellow esper. Fubuki highly respects Tatsumaki but believes she would be on top if not for her and Sweet Mask. Tatsumaki highly criticizes Fubuki for having followers and losing to Demonic Fan and Do-S but still saved her from both monsters. Tatsumaki believes her actions caused make her a great sister and is unaware of how strained her actions have made their relationship. While Tatsumaki is too proud to admit it she genuinely loves her sister.
Flash and Tatsumaki have unpleasant relationship with one another just like how she treats others S-class heroes. However, he appears to not be afraid of her and willing to scold her back whenever she insults him.
Despite his confidence in her power, Child Emperor greatly dislikes Tatsumaki's arrogant attitude and lack of strategical thinking since she thinks she can take on the entire Monster Association and Garou by herself to the point of berating the needs for a whole group S-class heroes as a support in the operation. While being polite from the outside, he is not above thinking her as a brat than an adult.
Genos has a strained relationship with Tatsumaki due to her smashing him through a wall several times or sending him flying away.
Tatsumaki seems to have some respect for Bang as she stood down when Bang told her to.
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.