The Reason Why Kaido is Immortal – His Lifelong Debt to Big Mom


With the recent information revealed in One Piece Chapter 907, I have a theory on what I believe the lifelong debt that Kaido owes Big Mom is.


As most people know, Big Mom is the current user of the Soul-Soul Fruit which allows her to more or less manipulate souls. The main part of her power I will be focusing on here to strengthen my theory is how she is able to infuse animals and objects with soul fragments in order to humanize them.

Although Big Mom is able to infuse animals and objects with soul fragments, she is not able to take soul fragments and put them into another human to theoretically increase their lifespan even though she is able to do the opposite in terms of decreasing it.


In Chapter 907, we learn that Kaido owes Big Mom a “life” long debt. I know this is going to sound crazy to you all right here. But what if the “life” long debt that Kaido owes Big Mom is actually life. This doesn’t make sense if Kaido were human, but what if Kaido is not human at all.


In the Whole Cake Island arc in Chapter 871, Big Mom refers to Kaido as a “Thing”. Not a human, but a “Thing”. There was a theory floating around a long time ago about Kaido potentially either having an Oni devil fruit or being an Oni himself. An Oni is a sort of supernatural ogre or troll that is very common in Japanese stories and folklore.

From that definition of what an Oni is, it does not sound remotely human whatsoever even though the Oni has a humanlike appearance. We have seen crazier things throughout the One Piece world so having a character who is a Oni is not out of the realm of possibilities.
If Kaido was not human at all, but instead an Oni or other type of beast, Big Mom technically could’ve given him soul fragments to extend his life. We have seen a beast/animal that received soul fragments in her crew already. That crew member is Crane Rider Randolph who was the rabbit homie we met in the Seducing Woods in the beginning of Whole Cake Island.

So more or less what I’m getting at here is that Kaido back in the day was actually some type of beast or an Oni, and Big Mom implanted someone else’s soul inside of Kaido’s body. This could be someone who was a heavy drinker based on the fact that every time we see Kaido he is always drinking heavily.

The biggest question that I’m sure is arising in your mind’s at this point in the theory is if Kaido was given a “humanoid” life by Big Mom, “Why can’t she just remove the soul she gave him in order to kill him?”. It would make sense since she is the holder of the fruit and can manipulate the souls she gives out to homies, etc. And in essence, Kaido would just be a big homie. To answer that question, I believe Kaido has eaten a devil fruit in addition to having those soul fragments placed inside of his body. The soul or spirit from the devil fruit could have mixed/mutated with the soul fragments given to him by Big Mom. With this mutation of the two souls/spirits, Big Mom would not be able to remove the fragments she originally gave to Kaido because they are not just those fragments anymore. She can’t remove the spirit/soul from someone’s body that has to do with their own individual devil fruit.

This would make sense in explaining why Kaido cannot die. This is because he has soul fragments placed into his body so that life can’t be taken away by just trying to kill yourself. In order to manipulate and remove that soul from his body, you would need something along the lines of what Brook did to the homies in Whole Cake Island. However, I don’t see Brook being nearly strong enough to remove that powerful of a soul from someone like Kaido. Especially if it has mutated with a devil fruit spirit.

This starts to become a problem in the story because if this is the case, how is he even going to be defeated? That part I am not sure of so we will have to see how that is handled in the story. With this whole idea of Kaido being a beast/animal and not an actual human, it makes sense why he would only want Zoan users as his crew. Since Kaido is an animal/beast himself, it makes him feel like he’s a part of the group and not some sort of outcast if he were the only one to not be fully human. I know this seems like a pretty out there idea for Oda to take this route, but I have very high hopes in this being true. HOPE YOU ALL ENJOYED!!!

*Theory by TallysTown

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