One Punch Man: How did Saitama get so strong?

Savannah Howard
Saitama in One Punch ManCrunchyroll

Saitama is perhaps the strongest – and most baffling – anime hero of all time. But what’s the true source of his immeasurable power?

One Punch Man’s Saitama is stronger than everyone’s wildest dreams. With just one punch, he’s capable of dispatching anyone who dares to face him, leaving fans and heroes alike wondering how he became so strong.

Although the true origins of his power are shrouded in mystery, there are enough morsels of information in the anime and manga to give rise to several fan theories.

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So, from radioactive bananas to a monster of a different kind, here are our favorite fan theories behind Saitama’s incredible feats.

One Punch Man: How Saitama thinks he got so strong

According to Saitama, the only way to get as strong as him is to train so hard your hair falls out.

When Genos, a human cyborg and Saitama’s protégé, asks how he became so strong, the explanation offered is too simple to believe: 100 push-ups, 100 sit-ups, 100 squats, and a 10km run every single day for over a year, until his hair fell out and he became stronger than every living creature in their universe.

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To most people, the workout routine sounds ridiculous. After all, who has the time or the drive to exercise that much every single day? But to Genos and the mad scientists from the House of Evolution, this explanation is as absurd as it is incorrect, as even the most dedicated athletes can’t come close to Saitama’s power.

Besides, Saitama has other abilities that can’t be explained by exercise alone. For example, he is capable of moving faster than the eye can see, he has survived fireballs and he can launch himself into outer space.

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So, what really happened? Let’s take a look at the top 3 theories ranked from least to most likely.

3. One Punch Man’s Saitama: Man or monster?

One popular theory is that Saitama isn’t a human at all, but a monster. After all, how else would he be able to walk away from creatures like Elder Centipede unscathed?

Obsessive training will never be enough to make you the most overpowered anime hero of perhaps all time – and neither will a love of bananas. This has led some fans to speculate that Saitama could in fact be a monster.

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In the One Punch Man universe, many heroes initially start as regular folks who’ve committed themselves to surpassing human limits. For instance, Blackluster attains superhuman strength through rigorous training, while Speed-o’-Sound Sonic, a ninja and assassin, consistently hones his strength, speed, and combat skills.

Additionally, humans can become monsters if they ingest – intentionally or not – monster cells. Throughout the series, it’s apparent that Saitama’s appearance has drastically changed since he first began training.

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With no other monster, human or alien coming close to matching Saitama’s extraordinary feats, could it be possible that Saitama is the ultimate human monster?

2. Blast is Saitama’s father/brother

A popular fan theory out there is that Blast, the highest-ranked S-class hero, is Saitama’s father or at least a close relative of some kind. That would explain Saitama’s extreme strength, although it still wouldn’t explain Blast’s.

Very little about Saitama’s past has been revealed in the manga or anime, leading fans to speculate whether his parents could also have extreme powers.

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So, could they be related? Clues in the manga, such as similar personalities and Blast’s wise counsel akin to Saitama’s unintentional wisdom, fuel this fan speculation. Plus like Saitama, Blast is a part-time hero who fights for fun, sporting a costume remarkably similar to our beloved One Punch Man.

Additionally, Blast’s notable absence in One-Punch Man season 2 suggests that he could play a much greater role in season 3 than any other S-class hero (besides Genos).

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3. Saitama removed his Limiter

The final fan theory, that Saitama removed his limiter makes the most sense (and is backed by the manga).

So, what is a limiter and how did Saitama remove his? In the manga, Dr. Genus from the House of Evolution explains that every creature has a growth limit, referred to as a limiter. If this limit is breached, the creature risks transforming into a mindless, rampaging monster. Therefore, it makes sense that Saitama became so powerful simply because he managed to remove his limiter.

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Does this mean that Saitama is a monster? The true answer to this is complicated. According to Dr. Genus, human transformation into monsters results from cellular anomalies triggered by environmental factors like bad habits, pollution, or intense rage.

In the manga, humans can surpass their limiters through near-death experiences, as seen in Garou’s battle-induced brush with death. Dr. Genus speculates that Saitama therefore managed to remove his limiter through an extreme training regimen bordering on death, with the only visible change being the loss of his hair.

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These three fan theories offer intriguing speculations about the origins of Saitama’s unparalleled strength, but they merely scratch the surface of the possibilities imagined by fans.

From hilarious notions like Saitama’s love of bananas triggering some kind of superhuman transformation to an encounter with a mysterious divine cube, the possibilities are as boundless as the One Punch Man’s power itself. So, while the truth about Saitama’s source of strength will probably remain unknown for a long time, which is your favorite theory?

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How to watch Crunchyroll from outside your location in 2023

Crunchyroll is the world’s best hub for streaming anime, whether it’s One PieceAttack on Titan, or Jujutsu Kaisen – and thanks to ExpressVPN, you can access the platform’s full library even if you’re outside the US.

If you’re abroad, here’s what you need to do to access Crunchyroll’s full selection – and it really is this simple: 

  1. Sign up for ExpressVPN, which has ultra-fast servers and offers a secure, private connection wherever you are in the world.
  2. Connect to a location anywhere in the US. Express VPN allows you to choose from 24 different spots, from New Jersey to Santa Monica.
  3. Visit Crunchyroll online and start streaming all of your favorite animes – and perhaps some you’ve never watched.

Accessing Crunchyroll’s US roster makes a difference. For example, Hong Kong users only have access to less than 100 titles, while the US has nearly 1,000 movies and TV shows. 

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You can also stream anime on Crunchyroll for free with an ad-supported plan. Or you can pay for a subscription – there’s even a 14-day free trial if you can’t quite make up your mind.

You can check out our other anime coverage here.

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About The Author

Savannah Howard is an Anime Writer at Dexerto. She loves dystopian thrillers, sci-fi and action series. You can email her here: