Saitama vs. Speed-o'-Sound Sonic

Saitama vs Sonic was the first battle between Saitama and the ninja assassin Speed-o'-Sound Sonic.

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

Battle
Sonic attacks Saitama mistaking him for a Paradiser because of his bald head, but Saitama easily catches his attacks. Due to his pride getting damaged, 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 it, and tries to finish off Saitama with his Wind Blade Kick. Unfortunately, Sonic is accidentally hit in the crotch by Saitama, ending their fight with Saitama the victor.

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 is his rival and declares he will one day kill Saitama. Saitama encourages him.

Trivia

 * The battle lasted 57 seconds.