Sonic is a unique character in One Punch Man in the way that he is neither villain nor hero. He is simply Sonic, he has no desire to destroy or take over the world and views the heroes with disdain. Sonic is a young male with a face that is rather feminine. He keeps his black medium length hair tied up in a topknot, and has large grey eyes. He is instantly recognizable by the purple markings under his eyes. He prefers to wear a tight black bodysuit. The body suit has rings or metal plating over his shins, arms, shoulders, chest, and waist. To finish it off he wears a long purple scarf. His weapons of choice are a ninjatō and other ninja equipment such as kunais and shurikens.
Sonic is egotistical and honestly believes that there is none faster than himself. He has a calm demeanor which he struggles to keep when he finds strong opponents that he can test his abilities on. When fighting against Saitama he struggles to stop smiling and calls this his “bad habit”. He is quick to jump to conclusions and even quicker to fight. He is rather persistent and will continue to engage against an opponent even when he realizes that the opponent is much stronger than he is. He also doesn’t care about what he needs to do to fight against whoever he views as a rival. Sonic has no issues with taking lives. He prides himself on the fact that he has never let a single target of his live. Although he views heroes as pointless he does not go out of his way to attack them. He believes heroes can’t win against any truly strong opponents and that they can’t truly protect anything.
We first meet Sonic while he is working as the body guard for Mr. Monier. Sonic has a rival relationship with Saitama which started the day that Sonic abandon Mr. Monier after Saitama ‘defeats’ him with an unintentionally well placed fist. Other than that it is unknown if Sonic has any relatives or friends at this stage.
Strengths and Weaknesses
Sonic’s best ability is his superhuman speed and his agility. As a ninja, Sonic is also adept at hiding his presence. He has high durability which is shown during his fight with the Sea-King. Sonic also has incredible strength despite his frail appearance. However his belief that he is the fastest and that no one can catch up or meet his speed is his downfall that and he often underestimates his opponents.
In The Anime:
As mentioned before we meet Sonic while he is working as a bodygaurd. This enabled him to meet Saitama. Through fighting Saitama, Sonic finds a new rival and leaves his job as a bodyguard. The next time Sonic meets Saitama he forces him into a fight by destroying buildings and endangering civilian lives. At the end of that fight Sonic is viewed as a villain and placed in jail. Once in jail he quickly defeats all the inmates and quickly breaks out again. However once he is free he bumps into the Sea-King but he doesn’t have his weapons. Unknowingly to him he helps in the battle against the Sea-king as he provides some much needed extra time for the heroes. After escaping the Sea-King (naked), Sonic rushes off to fetch his clothes and weapons so that he can properly fight against the Sea-King. However by the time Sonic returns the Sea-King had been defeated. Sonic then goes on to challenge Saitama again but instead goes against Genos, who seems to be on equal footing with Sonic. Thus showing that Sonic fights at a S-Class hero level.
Sonic provides comedy and is a character that can pretty much do what he likes as he does not need to follow the main plot of the anime. Sonic has a lot of room to grow in regards of character development where we can learn why he believes heroes can’t protect anything and he has the potential to really improve his skills each time he faces Saitama.