Saitama vs. Speed-o'-Sound Sonic

Saitama vs Sonic (F-City) is the first battle between Saitama and the assassin Speed-o'-Sound Sonic.

Prelude
Realizing that Hammerhead escaped, Sonic hunts after his trail only to encounter Saitama.

Battle
After defeating Hammerhead, Sonic attacks Saitama mistaking him for a Paradiser. Due to an injured pride, Sonic tries to kill Saitama for being able to see through his attacks. He showcases his speed, boasting how Saitama can't keep up with his speed, and tries to attack Saitama with his Wind Blade Kick. Unfortunately, Sonic is accidentally hit in the crotch by Saitama, ending their fight.

Aftermath
While writhing in pain, Sonic declares that he will take a leave from his mercenary occupation to train and asks for Saitama's name. Sonic states that Saitama his rival and declares he will one day kill Saitama. Saitama encourages him.