From the very start of Kaido’s introduction, we have known that he has been defeated as a pirate seven times, been captured by the Navy or his enemies around 18 times and has lived as a prisoner before. Kaido was tortured over a thousand times and was sentenced to death forty times and yet nothing done to him was able to kill him. From that introduction, we can surmise that Kaido was in his enemies hand’s for a significant amount of time. What we have yet to have revealed beyond why Kaido is so “unkillable” is where and when exactly he was held as a prisoner and by whom. When looking at what has been featured so far across the story since Kaido’s arrival onto the pages, I find myself compelled to believe that at one point in Kaido past, over 33 years ago, he was held as a prisoner on Punk Hazard and experimented on.
There are four main reasons for why I believe Kaido was a prisoner of Punk Hazard. The first is type of research that we know was conducted on Punk Hazard in the past. The second is the “Numbers” and their connection to Punk Hazard. The third is the artificial Devil Fruit Vegapunk created. And the fourth reason is Big Mom and her knowledge of Punk Hazard.
The research done on Punk Hazard in the past:
Featured during the Punk Hazard Arc were experiments involving gigantification, dragons and artificial devil fruits (in particular Vegapunk’s artificial Devil Fruit). What do all of these experiments have in common once you look at the resulting consequences of those experiments? Lets first look at the results of the experiments. Starting with gigantification, we have the failed Ancient Giants that the World Government Science division tried to recreate. Next are the Dragons that Dr. Vegapunk created; Dragon Number Thirteen and the smaller version of the Dragon. And finally, there is the Artificial Devil Fruit produced by Dr. Vegapunk which Momonosuke ended up consuming giving him the ability to transform into a Dragon. Looking at those experiments, the two main themes are Ancient Giants and Dragons. Who do we know that has connections to both? Kaido.
While it is not at this point in time confirmed, Kaido’s design conveys that he has similarities with the Ancient Giants currently shown – Oars and Little Oars Jr. There is the size difference between Kaido and Oars/Little Oars Jr but Kaido may be a very unique variant of the Ancient Giant or could be only part Ancient Giant. Kaido’s younger self silhouette from his Rocks Pirates days showed him with Ancient Giant-type horns at that time. For that reason, I do not believe Kaido had Ancient Giant DNA injected into him while being experimented on but rather I believe Kaido was linked to the Ancient Giants from birth through his blood. Yamato inheriting the horns also leads me to believe it is a natural genetic feature in their blood. Kaido’s DNA was used by the Punk Hazard scientist to research their experiments on recreating Ancient Giants. In addition to the connection with the Ancient Giants, Kaido has the ability to transform into a Dragon through his Devil Fruit. Likely before being captured, Kaido would have already had his Mythical Dragon Zoan Devil Fruit power.
The Numbers and their connection to Kaido:
Turning to the Numbers, they were part of Kaido’s forces 20 years ago when the Kozuki clan were defeated as Jaki was present during Oden’s flashback when he captured Inuarashi and Nekomamushi. What this means is the World Government were conducting experiments on Punk Hazard trying to recreate the Ancient Giants over 20 years ago. What I imagine happened is the World Government scientist used Kaido’s DNA as the foundation for experimenting on the prisoners they had as test subjects in the facility. The Numbers would have been created after Kaido escaped Punk Hazard. As such, the “Numbers” ended up developing certain features and tendencies similar to Kaido, mainly the horns and the love for alcohol. Kaido and the Numbers also share in the use of the same type of weapon – kanabō. Kaido may have required the Numbers to wield kanabō or it could have been a conscious choice by the Numbers derived from their connection to Kaido. I would presume the latter. The failed nature of the experiments would likely explain their simplistic cognitive functions and inability to engage in any lateral thinking. Someone in the World Government could have put these experiments up for sale in the black market which Kaido ended up purchasing as Big Mom mentioned.
Lets take that one step further. In addition to the Numbers, I can see Dragon Number Thirteen and the smaller dragon being based on Kaido’s DNA. The naming convention of the Numbers and Dragon Number Thirteen suggest some connection regardless of the Dragon being named by a Tenryuubito. Once Dr. Vegapunk joined the World Government, which would have been after Kaido escaped, he could have used the research and samples on Kaido to conduct his experiments on gigantification (Ancient Giants) and on his own research involving dragons. Considering the “[G]IANTS” titled book in Vegapunk’s research room containing many sticky tags (bottom left of the below image), it appears a lot of effort was spent by Dr. Vegapunk on that project.
Ultimately though, Dr. Vegapunk was unsuccessful in his gigantification experiments (Numbers?) though he did succeed in producing dragons via Dragon Number Thirteen and the smaller version Dragon. Dr. Vegapunk has already shown his capability in isolating Devil Fruit powers by utilising the Pika Pika no Mi to develop the explosive lasers for the Pacifista. He may have first attained that knowledge through the experiments done utilising Kaido’s DNA samples and research. The reason the Dragons survived the Shinokuni poison from four years ago when Caesar activated his weapon and the battle between Sakazuki and Kuzan could be the result of having Kaido’s DNA. The DNA would have also allowed those experiments to breathe fire and attain their thick skin.
And even beyond that, there is the possibility that Queen and King were also prisoners on Punk Hazard being experimented on. With Queen, that scar running down his right shoulder and chest could be the result of experiments, particularly because of its stitched nature. Queen may have also developed an interest in weapons and viruses because of his exposure to the World Government science labs. King is an interesting case due to the rare race he belongs to but I wonder if the experiments done on him caused his wings to turn black and to produce the plume of fire rising from his back. King and Hitetsu belong to the same race but unlike Hitetsu who has white wings, King has black, why? If we presume Hitetsu is what the natural look of the race is and if we take into account the appearance of King, it seems likely that King may have been experimented on. The experiments on King could have caused an issue with his skin which is why he now covers his whole body and wears a full-faced mask. King’s suit could be something he acquired from Punk Hazard. Additionally, if Dr. Vegapunk had access to King’s DNA samples, he may have used it in conjunction with Kaido’s DNA to help add wings to the Dragons he created. As a result of Kaido freeing the two of them, they may have swore their allegiance to him and been the start of the Beast Pirates.
Dr. Vegapunk’s Artificial Dragon Devil Fruit:
Another piece of evidence that leads me to believe Kaido was at one point imprisoned on Punk Hazard is the Artificial Devil Fruit Dr. Vegapunk created. The resemblance in Kaido’s and Momonosuke’s Dragon transformation seems too homologous to be coincidental. I believe Kaido’s DNA (including his Dragon aspect) was used as the base to create a Dragon which in turn was used to create the Artificial Devil Fruit. If the research and DNA samples of Kaido were stored on Punk Hazard, it makes sense why Dr. Vegapunk would conduct his research on the Artificial Devil Fruit there. Dr. Vegapunk would have likely used his (and Judge’s) findings on the Lineage Factor to isolate the Dragon aspect of Kaido’s Devil Fruit via the DNA sample to base his research on the Dragons and eventually the Artificial Devil Fruit project.
It is unclear whether the Artificial Devil Fruit Dr. Vegapunk created was a failure as the only commentary we had on that devil fruit were the Punk Hazard subordinates stating they heard the devil fruit was a failure. At this point in time, there haven’t been any major side-effects besides Momonosuke transforming into a Dragon when he is scared. Compared to the SMILEs, Dr. Vegapunk’s Artificial Devil Fruit is much more comparable to a real Devil Fruit. The dragon transformation of Momonosuke’s is definitely smaller than Kaido’s but that could be due to Momonosuke’s age, lack of control over the Devil Fruit power and being human. If Kaido is connected to the Ancient Giants, that may have influenced his Dragon transformation. I don’t believe the Artificial Devil Fruit created by Dr. Vegapunk was a complete failure, it may not have been perfected but from what has been shown, I cannot see any failings in its functionality. The Artificial Devil Fruit was likely left behind because Dr. Vegapunk was unable to retrieve it when fleeing Punk Hazard due to the poisonous gas spreading through the Island. Caesar jealous of Dr. Vegapunk likely considered the Artificial Devil Fruit a failure because he could not bring himself to admit that it may be a success and that could be where the Punk Hazard subordinates heard the information from.
Big Mom’s relevance to Punk Hazard:
I believe it was Big Mom who helped free Kaido from Punk Hazard. Big Mom had mentioned to Kaido before leaving for Wano Kuni of a debt Kaido owes her from the past. Could the debt she is referring to be the time she saved him from the World Government Science research facility stationed on Punk Hazard? That certainly would count as something Kaido would owe Big Mom big time for. If this is the case, this could explain why Big Mom knows about the Punk Hazard research such as the gigantification experiments. They were part of the same crew prior to the God Valley incident, so before their relationship eroded into what it is today, Big Mom may have felt desire to help Kaido as a result of the kinship they once shared.
Big Mom’s time on Punk Hazard may have also been where she attained a copy of the Punk Hazard lab blueprints. Additionally, during the attack to free Kaido, Big Mom may have also learned of King and the race he belongs to, assuming King was one of the subjects held and experimented on at Punk Hazard while Kaido was there.
As for how Kaido ended up being captured in the first place, I would expect that during the events on God Valley, Rocks betrayed his crew in an attempt to escape when he realised they couldn’t defeat Roger and Garp and as a result of that betrayal, Kaido was captured by the Marines and taken to the World Government research facility on Punk Hazard. Since that moment, Kaido’s perception of pirates and the world became warped.
With Punk Hazard holding much relevance to the science experiments conducted within the One Piece world including the Numbers, SMILEs and possibly Seastone Chains which are connected to the Beast Pirates, it seems appropriate for Kaido to also have a direct connection with Punk Hazard. Knowledge of the research done by the World Government scientist could have been acquired by Kaido through his time as a prisoner and research subject there. Additionally, Big Mom’s knowledge of Punk Hazard and her relation to Kaido also suggest a connection there which could be linked to the debt Kaido owes her. Kaido being a prisoner on Punk Hazard does appear to tie those elements together.