Saitama vs. Flashy Flash

If you lose, you will become my student and obey me.'''

Battle
The instant Flashy Flash declares the start of the fight, Saitama closes the distance between them and almost catches the ninja with his right hand. After keeping a distance from Saitama, Flash admits how he has let his guard down due to Saitama's nonchalant personality before deciding to immediately go all-out against him. Charging at Saitama with his Dragon Thurst Kick, Flash hits him frontally with a double kick. When Saitama throws a punch in an attempt to retaliate, Flash manages to avoid the punch by using his Spinning Top Slide to rotate and swerve himself out of the way.

Flash proceeds to unleash a series of his ninjutsu techniques on Saitama; first striking him with both of his open palms using Falling Moon Palm, followed by his Misty Mantle which distracts Saitama with his cape before using Falling Leaves Barrage to attack him with a salvo of open-hand slaps in order to seemingly obscure his view. Flash continues his onslaught by attacking Saitama with his Wind Blade Kick from above and follows by using his Blue Tempest Fist to land a barrage of punches on Saitama, who is completely unfazed nonetheless. Finally using his Flowing Shadow Feet to seemingly accelerate his speed, Flash charges at Saitama with his Flash Fist, attempting to land a powerful and solid punch on him in the face. However, before his punch connects, Saitama throws a punch of his own that passes Flash's from below and almost hits him. This leaves the S-Class hero shocked and frozen as Saitama stops his punch when it is mere inches away from the head of Flash. At that exact moment, Genos interrupts the fight by announcing there has been a monster alert.

Trivia

 * In contrast to the manga, the fight lasted noticeably longer in the original webcomic.