Speed-o'-Sound Sonic

Speed-o'-Sound Sonic, often called simply Sonic, is a recurring villain and occasional anti-hero, a former member of the Ninja Village's 44th graduation class nicknamed The End. He first appeared as a bodyguard hired by Zeniru, and has since declared himself Saitama's eternal rival.

Despite an outwardly calm demeanor, Sonic loves fighting and is driven by bloodlust, competitive pride, and the thrill of facing opponents he might not beat. His ego runs enormous — once he decides to kill someone, he refuses to stop until he succeeds, and he holds real disdain for the world, especially heroes, whom he considers unable to either win real fights or truly protect anyone. Beneath that cynicism, though, he has a softer side, revealed during the period he trained specifically to challenge Saitama.