Sonic is a villain in the series, first appearing as a bodyguard hired by Mr. Monier. He views Saitama as his eternal rival.
Sonic is a villain who, despite his normally calm appearance, loves fighting strong opponents as shown by when he gets a "child-like smile" on his face when he first meets Saitama and has two of his attacks blocked, earlier calling this his "bad habit." He seems to be very quick to act as he attacks Saitama on their first meeting without letting him explain the situation.
