Sonic Speed-o'-Sound, often known simply as Sonic, is a recurring character in the anime series One Punch Man. He is a skilled ninja and a self-proclaimed rival of the protagonist, Saitama. Sonic is characterized by his incredible speed, agility, and ninja techniques, making him a formidable opponent. Despite his antagonistic role, Sonic is not truly evil but rather obsessed with defeating Saitama to prove his superiority. His persistent drive and unique abilities often lead to humorous encounters with Saitama, who easily defeats him with a single punch.