Flashy Flash/Synopsis

History
Flashy Flash was trained in the Ninja Village and participated in the 44th class along with Speed-o'-Sound Sonic. Upon graduation, he was the strongest member of his class, but caused an incident that left Sonic the only other survivor of their class and effectively ruined the village according to Gale Wind.

He left the village after some time. For some unknown reasons, he was hunted by multiple assassins and criminal masterminds but he managed to dispatch all of them during his spare time in his hero's activities. Some criminals and assassins Flashy Flash killed include Aburabozu, the king of organ traders, Harold the drug kingpin, heart collector Burigura, phantom thief Chimagusa, the invincible pirate captain Devil Storm and the higher ups of the Coalition of Assassins.

Alien Conquerors Arc
Flashy Flash appears at the S-Class Hero Association meeting. Although he was at the meeting, he remained quiet for the majority of the meeting. When the Dark Matter Thieves attacked, he left the scene along with other heroes.

Super Fight Arc
Flash appears in I-City where he assists the gathering heroes prepared to fight against Hundred-Eyes Octopus. He uses his powerful speed to rush toward the monster and stabs one of its eyes. After that, he proceed to slash all the eyes of the monster until it goes berserk. As Flashy Flash begins to unleash his special technique to finish the monster for good, Tatsumaki comes in time, lifts the monster up in the air and crushes it into a giant ball.

After the death of the monster, he and the others heroes are berated by her. However, he also proceeds to berate her back, but is stopped by the other heroes. The heroes end up parting ways for now.

Monster Association Arc
The S-class heroes, Flashy Flash, Tatsumaki, Child Emperor, Pig God, Kamikaze, Superalloy Darkshine, Zombieman, Puri-puri Prisoner and Sekingar attend a meeting and they reassure Narinki that they will rescue his son. They each receive a transmitter that will show their location to each other.

The meeting continues as they plan out their attack on the Monster Association. Flashy Flash gets into a argument with Tatsumaki before Sweet Mask barges into the meeting. When Sweet Mask demanded to take leadership over the S-Class heroes, Flashy Flash taunts Sweet Mask to try and take control with force. Before the argument could escalate further, King arrives and settles the situation. Flashy Flash is suitably impressed with King overnight monster elimination at Z-City. When Sweet Mask backs down, Flashy Flash sighs. Flashy Flash leaves with various other heroes to attack the the Monster Association.

Flashy Flash arrives at the ghost town of Z-City with various other heroes. He compliments Shadow Ring on her ninjutsu and asks where she learned them. Shadow Ring replies not from the same place as Flashy Flash she skitters off. Flashy Flash mentions that it couldn't be his ninja village as his village doesn't train any woman. Flashy Flash kills various monsters from the initial monster attack. After dealing with the monsters on the surface, Flashy Flash heads underground into the Monster Association base alone. There he dispatches several monsters before being confronted by Hellfire Flame and Gale Wind.

The monsters compliment Flashy Flash on his speed before they do battle. During the fight, Flashy Flash destroys the corridor, and Gale Wind rotates one of the blocks they were standing on in order to battle in a more open area. As they fought, Gale Wind explains that they will eliminate all foes who are possibly a threat, and explains the purpose of going after Flashy Flash was because he viewed other ninjutsu masters as rather troubling. Flashy Flash sprints off at speeds neither monsters could track, and he then tells them to unleash their full power as monsters.

Eventually, they are both forced to reveal their monster forms after realizing they are outclassed in their human forms. Flashy Flash's eyes widen in surprise at their increased speeds, and is barely able to block both of their attacks. Round 2 of the battle between the three ninja then begins. They continuing battling, and the two monsters are able to pressure Flashy Flash, managing to make him cough up blood, but once the hero became serious, he strikes both of them with a series of kicks, and then slices both of them in half, ending their lives.

Flashy Flash leaves the battlefield and arrives at a junction. He goes to consult his Locator to see where he is but finds that he lost it in the battle.

Monster Association Arc
He meets up with Saitama, who he mistakes for an enemy. He was very surprised when Saitama was able to dodge and counter his extremely quick attacks. They finally get to where the fight with Garou was going on. Along with Darkshine, his true speed and abilities were shown. He left his mark as perhaps one of the fastest characters in the series, but was ultimately defeated. During their attack on Garou, Zombieman states that even the strength of Darkshine and speed of Flashy Flash would not be enough.

Fall of the Hero Association Arc
By the time the Hero Association was about to fall, Flash acknowledges Saitama's strength, having been among the few heroes who were still conscious during the conflict with the awakened Garou, whilst also feeling that Saitama needed a proper teacher in order to show him how to fully hone his strength.