Flashy Flash/Relationships

Metal Bat
They had limited interactions during the anime and OVA. However, neither of them could get along with one another. In both moments, Flash would instigate a verbal conflict whenever Metal Bat is talking. This usually ends with Flash mocking Metal Bat and Metal Bat's temper escalating the conflict between them.

Superalloy Darkshine
While there was never a true interaction between the two, Darkshine and Flash are known to be a dangerous combo in battle. The two stood together against Garou alongside Puri Puri Prisoner.

Saitama
Flash mistook Saitama as a monster and the two had a brief scuffle. After clearing the misunderstanding, the two became acquaintances with one another, with Flash acknowledging Saitama's superior abilities.

After being defeated by Garou, Flash was one of the few who retained consciousness and witnessed Saitama defeating Garou. In addition to acknowledging Saitama's strength, Flash decides that Saitama needs a teacher to polish his strength. However, because of his assassin's instinct and mindset, he still looks down on Saitama since he feels that Saitama wastes a lot of his athletic potential and lets his guard down, giving his opponents an unnecessary chance to strike him.

Tatsumaki
Flash and Tatsumaki have an unpleasant relationship with one another, just like with other S-class heroes. However, he appears to not be afraid of her and is willing to scold her back whenever she insults him. At one point, he insults her powers, saying they halted her physical and mental growth.

Gale Wind and Hellfire Flame
Gale Wind and Hellfire Flame came from the same Ninja Village. The two monsters graduated at the 37th class making them an upperclassmen to Flashy Flash. The two ninjas desired to kill Flashy Flash due to his ninjutsu talents and causing an incident that killed the majority of the Ninja Village 44th graduation class known as "The End".

Though he initially mocked the two ninjas, by the end of the fight he displayed some respect towards them, remarking that they might have caused the other heroes more trouble had either of them escaped because of their speed.

Sweet Mask
Flashy Flash does not like Sweet Mask's authoritative and egotistical attitude. While he has some disdain towards some of the S-Class heroes, the tone he gives off is either of annoyance or even teasing, as seen with his interactions with Metal Bat. Flash's displeasure towards Sweet Mask goes to the point of eliciting his murderous intent towards the fellow hero. He goes out of his way to instigate a challenge against Sweet Mask.

Shadow Ring
The two are trained in seperate arts of ninjutsu while employing themselves into the Hero Association. Shadow Ring is one of the few heroes Flash shows any respect towards. He complimented Shadow Ring's ninjutsu, even asking her for details to her technique. For Shadow Ring, she is very impressed with Flash's speed. Flashy Flash later on notes that ninjutsu not only comes from his village but also other places, using Shadow Ring as an example.

Speed-o'-Sound Sonic
Speed-o'-Sound Sonic was Flashy Flash's classmate in the 44th class during his time as a trainee in the Ninja Village. Their relationship so far is unknown but Flash is responsible for making him the only survivor of the 44th graduation class. During the conversation with Gale Wind and Hellfire Flame, Sonic shows no ill-feeling toward Flashy Flash.

In the Original Webcomic, it is revealed that the two were actually friends. When Flash was practicing techniques, Sonic decided to approach him and they became friends who relied on each other to keep their sense of morality during the brutal training of the village that encouraged the complete removal of all emotions. The two ninjas bonded, with Flash noting that talking with him allowed him to recover his emotions lost from the Ninja Village training, making it a good experience for him. They both shared a sense of justice and desire to change the institution of the Ninja Village.

When Flash went on a killing spree and destroyed the entire village, he tried to poison Sonic's tasteless stew rather than brutally murdering him like everyone else as a mercy kill. He notes that as he and Sonic were two of the worse students, they had endured even harsher training than others, which is why Sonic is still alive. When Flash found out about Sonic's survival until now after being exposed to the outside world and the bounty on his head (as he is an S-Class criminal), he chose not to hunt him, indicating the strength of their previous relationship.