Speed-o'-Sound Sonic is One-Punch Man's resident anti-hero/pseudo-villain/Saitama rival. The ninja is first introduced as Zeniru's bodyguard but quickly becomes relevant to the story as a whole. Like most of the characters in the series, Sonic derives pleasure from fighting powerful opponents.

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Unfortunately, being the protagonist's rival means he'll never be more than second-best and that frustration drives Sonic's entire arc. He has become a fan favorite, but casual viewers might not be aware of how intriguing the troublemaker actually is. Here are 10 weird facts you never knew about One-Punch Man's Speed-o'-Sound Sonic.

10 He Acquires His Weapons In A Shockingly Normal Manner

Speed-O-Sound Sonic's sword breaking

Speed-o'-Sound Sonic is always prepared for battle, whether he's armed or not, but nine times out of ten you'll find him wandering around with his token ninjatō. He's also known for carrying kunai and special shurikens that either explode on impact or provide a smokescreen for cover.

Most ninjas are so formidable that no one ever stops to ask this one very valid question: Where do they get all those weapons from? The answer is more reasonable than you'd expect, at least in Sonic's case. He buys them from a weapons shop. Simple as that.

Speed O Sound Sonic One Punch Man feature

Sonic's distinct look could partly be attributed to his hair or outfit, but the purple marks under his eyes are typically considered his most distinguishable feature. However, these aren't unique ninja marks with some obscure or special meaning. They were actually inspired by sports — American football, to be exact.

In that same vein, the marks also serve as a reference to Eyeshield 21. The American football series is illustrated by Yusuke Murata, who is the artist behind the redrawn One Punch Man manga.

8 He Can Cook

Sonic's culinary skills were displayed in the One Punch Man anime during a humorous sequence where he cooked a monster cell. The scene is also present in the manga, though the meal arguably looks better in color.

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This doesn't necessarily make Sonic a top chef, but it must require some level of talent to make a monster cell look edible. On top of that, he paired the plate with a glass of red wine, which is known to complement most meats. The man knew what he was doing.

7 He Misinterpreted The Reason Behind His Weight Loss

This fun fact correlates with Sonic's aforementioned culinary skills because, in his attempt to become a monster, the ninja actually gave himself stomach problems. Monster cells are meant to be consumed raw, so cooking them negates their effects (and sends you to the toilet, apparently).

Sonic's diarrhea was so intense that he ended up losing about 2 kilograms — approximately four and a half pounds — in the process. He presumed that the weight loss was the result of his "monster transformation". The reality is that the cell did absolutely nothing besides help him trim a few pounds.

6 A Fight Between Sonic And Genos Would Be Inconclusive

Speed-o'-Sound Sonic and loyal Saitama disciple Genos have already crossed paths in the storyline. The two sparred for quite a while before being interrupted by the main character. It appeared that the cyborg had been defeated, but series creator ONE insists otherwise.

ONE has stated that a fight between Genos and Sonic would ultimately end in a draw and not a victory for the ninja, as the season two showdown insinuated. We'd like to file a petition for a rematch, please.

5 He Was Quite The Troublemaker In Prison

An extra chapter within volume four of the One Punch Man manga titled "Prison" gave some insight into Sonic's life behind bars. Spoiler alert: It was a chaotic mess. To be fair, the detention facility he was confined in was home to some of the most savage criminals around.

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Sonic told the other prisoners that he would kill them all and proceeded to fight them one-on-one. This displeased the prison's boss and everyone did their best to correct their behavior... besides Sonic, of course.

4 He Could've Defeated The Deep Sea King...Sort Of

The Deep Sea King was a fearsome being that gave almost every hero that confronted him a nasty beatdown. Sonic held his own for a respectable amount of time, but he couldn't gain the upper hand on the creature. Nonetheless, ONE has confirmed that Sonic could've emerged victorious from this encounter... with a few stipulations.

For starters, Sonic was fresh out of prison when he faced the monster, so he didn't have any of his usual weapons on hand. He would need them for his hypothetical win. Secondly, Deep Sea King would have to be in his dry, pre-rain form to be conquered by the ninja.

3 He Bonded With A Baby Boar

"The Ninja Who Is Too Complicated" is the third OVA of the One Punch Man series and many fans might have missed the extra episode. We're introduced to an adorable baby boar named Ino who becomes Sonic's right-hand piglet for a while.

The boar becomes fond of Sonic after the ninja saves him from a massive snake. The duo trains together and the relationship is documented in a sweet training montage. After Sonic leaves, Ino stays with an acquaintance named Frank.

2 His Physical Appearance Serves A Greater Purpose

Speed O Sound Sonic One Punch Man

Saitama's appearance is underwhelmingly average for such an overpowered character. It's a running joke within the series, but what you might not know is that Genos and Sonic were specifically designed to look much cooler than him.

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ONE intended to use physical appearance to add a gap between Genos/Sonic and Saitama. However, Yusuke Murata's incredible drawings multiplied that gap in an unforeseen manner. Thus, the ninja and the cyborg ended up looking miles more impressive than the most powerful human in the series.

1 He Has Nightmares About Saitama

As illustrated in the aforementioned OVA, "The Ninja Who Is Too Complicated", Sonic is so scarred by his loss to Saitama that he literally has nightmares about him. In the extra episode, Sonic trains to become stronger and aims to rid himself of said nightmares by defeating the protagonist.

As expected, he has yet to experience the victory he so eagerly desires. Perhaps he should focus on besting Genos first, especially since ONE claims that they're equal in terms of strength.

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