|Genos vs. Speed-o'-Sound Sonic|
|Chapter(s)||41, 42, 43|
|Outcome||Interrupted by Saitama|
|Hero Genos||Villain Sonic|
|Genos is uninjured||Speed-o'-Sound Sonic is uninjured|
|Previous||Garou vs. Blue Fire, Heavy Tank Fundoshi, Magic Trick Man and Criminals|
|Next||Saitama vs. Fubuki, Eyelashes, and Mountain Ape|
Genos is with Saitama at their apartment, when he feels someone coming towards them. While checking outside, he discovers Speed-o'-Sound Sonic. Sonic claims to be Saitama's rival and wants to fight him. Not wanting to disturb his master, Genos challenges Sonic himself.
They begin their battle and are shown to be on equal footing, with Sonic being too fast for Genos, and Genos being too durable. As Genos tries to attack Sonic, the impact accidentally catches Fubuki in her fight with Saitama. Genos apologizes to Saitama for the damage and recognizes Fubuki, misinterpreting her position as a failed attempt at taking down Saitama, when Sonic attacks Genos with his Exploding Shurikens, which prove to be ineffective.
Sonic declares that he shall defeat Genos and challenge Saitama to another duel, but Genos simply states he will make sure Sonic will be erased. Sonic, amused by Genos' statement, is suddenly attacked, and begins to dodge all of Genos' attacks, all the while feeling mocked, until Genos cuts off his topknot. Genos then gets behind Sonic and uses Machine Gun Blows, but is surrounded by Sonic's Four Shadows Burial. Just as Sonic is about to attack Genos with his Scattered Flash Slash, Genos decides to blast the whole area with his Incineration Cannon, but is knocked down by Saitama who didn't want his place to be destroyed.
Saitama intervenes in the fight, scolding Genos for not having any reason to fight Sonic. Saitama then decides to fight Sonic seriously, to which Sonic declares he will show his newly developed technique.