Speed-o'-Sound Sonic vs. Flashy Flash

I always wanted to settle the score with you someday.'''

Prelude
After receiving a letter of challenge, Flashy Flash splits up with Blast and Saitama to meet with Speed-o'-Sound Sonic at the location given on the letter of challenge. This location is the place Sonic dreamed of putting his own ninja village, which had now become an illegal dumping sight. It is now referred to by Sonic as "The place where dreams end."

Battle
Flashy Flash and Speed-o'-Sound Sonic draw their swords, and both take identical battle stances. The two exchange remarks and Sonic tells Flashy Flash not to get cocky, as he's the one who taught Flashy how to use a blade. After a brief flashback, Sonic and Flashy Flash charge at each other, their swords colliding. After a brief scuffle, the two ninjas jump away from each other, with Sonic taking the opportunity to throw three Exploding Shurikens. Flashy Flash prepares to defend himself, but Sonic rushes behind him and throws three more shurikens. Flashy Flash leaps in the air to avoid the attack, and Sonic seizes the opportunity to surround Flashy Flash with afterimages using his Ten Shadows Funeral technique, with them all attacking Flashy Flash with Wind Blade Kick simultaneously. Flashy Flash deduces which Sonic is real and blocks his kick with his forearm guards. He then retaliates with his ultimate technique, Flashy Kicks, launching Sonic into the ground. Flashy Flash praises Sonic for being able to force him to use an ultimate technique, before dodging a bombardment of weapons from the Heavenly Ninja Party.

Aftermath
Their battle was cut short by the Heavenly Ninja Party's attempted surprise attack on Flashy Flash. Sonic gets up from Flash's Flashy Kicks with minimal damage taken and attacks one of the heavenly ninjas. The Heavenly Ninja Party agrees that Sonic is a traitor and claims they will excute both him and Flash. Sonic mentally compares the ninja group to Saitama, claiming that they are smaller than grains of sand. Sonic stands up, claims he's sick of them acting better than him just because they are his seniors. Flashy Flash and Sonic agree to postpone their duel and work together to defeat the Heavenly Ninja Party.

Trivia

 * In contrast to the manga, the fight lasted noticeably longer in the original webcomic.
 * In the original webcomic, both Sonic and Flash used different techniques and the fight was different too, the only similarity is that the outcome of the fight is still the same.