Introduction: Zunisha is an enormous elephant that has lived for over a thousand years. Some time in the distant past, he was punished for a committing a crime and was not allowed to do anything but walk for eternity unless some gives him an order to do something else.
For some reason, it seems like his voice can only be heard by a few people (Roger, Oden, Luffy, Momonosuke) but only Momonosuke was able to issue any orders to it.
Hypothesis: Zunisha was given an important task by none other than Joy Boy, however he failed and was banished from his homeland and was to act only on orders given by specific people and was also to carry and protect the Mink Tribe for several hundreds of generations.
Elaborate Theory: Before I get into the meat of the theory and what Zunisha’s task was, a little recap to refresh our memory.
Joy Boy made a promise to Poseidon a.k.a the Mermaid Princess (of that time) which involved using her powers to raise the giant ship Noah to the surface. However, for some reason he failed and wrote an apology to Poseidon and the Fishmen who promised to keep Noah safe until a certain day.
Now to begin my theory, I believe that Joy Boy’s promise was to bring all the Fishman from below the see to the surface world with the help of Noah.
Part 1: Noah was built in the Ancient Kingdom or Wano upon the order of Joy Boy
As we all know, both the Ancient Kingdom and Wano were technologically advanced in the past, the Ancient Kingdom for the weapons, Wano for the Poneglyphs. Pluton is an enormous battleship built by those in the Ancient Kingdom so we do know they were capable of building large ships. We also know that Wano had some close connection to the Ancient Kingdom, they were most likely allies. Seeing that Wano helped with passing down information with the Poneglyphs, they may have also helped build Noah.
The Ancient Kingdom and Wano were planning on bringing the Fishmen to the surface to help them with the war against the 20 kingdoms. The Minks were already allied with the Ancient Kingdom and Wano at this point. Once the Fishmen were brought to the surface safely, they would form a powerful combined army to fight against the 20 kingdoms.
This was however, a very precarious plan. The 20 kingdoms would be ready to sabotage their plan if it wasn’t executed properly.
Part 2: Zunisha was tasked with delivering Noah to the Fishmen and also bringing it back
Zunisha, the enormous elephant, was either from Wano or the Ancient Kingdom originally. He was already a well established servant of his kingdom (again, it could be either the Ancient Kingdom or Wano). Joy Boy had a very close relationship with Zunisha and viewed it as one of he most stalwart subjects. So when Noah was finally built, he entrusted Zunisha to take it from where it was built to Fishman Island where Poseidon would use her powers to order the Sea Kings to receive Noah and bring it down so the Fishmen could board it. He was supposed to wait for a few days and when all the Fishmen have boarded the ship and bring Noah to a certain location. All this was to be completed in a given time-frame failing to do so meant the entire plan had to be forfeited as their enemies would’ve advanced to far.
Here is a detailed flowchart of Zunisha’s task:
Part 3: Zunisha returns empty-handed
For whatever reason, possibly due to the involvement of the enemies of the Ancient Kingdom, Zunisha forgot about his task and returned to the Ancient Kingdom/Wano several days later, by which point Joy Boy and Poseidon’s plan had already failed, without Noah. A shocked and enraged Joy Boy admonished Zunisha for its grave blunder.
The Ancient Kingdom and Wano are now in a pinch. With 20 kingdoms and their powerful forces approaching rapidly and without the additional support of the Fishman and Poseidon, they were bound to fail and lose the war. As a last resort, they decided to preserve the knowledge and ideals of the kingdom even if it meant being shrouded in darkness for several hundreds of years. The Ancient Kingdom was destroyed, but their allies, Wano, the Minks, etc. remained, separate and away from the World Governemt. This is explains why both the Minks and Wano seem to have little to no contact with the World Government.
Part 4: Redemption, Momonosuke, and Lady Toki
For Zunisha to atone for his blunder, Joy Boy ordered it to carry the Minks on its back along with one or more Poneglyphs in order to preserve the knowledge of the Ancient Kingdom and its ideals and walk for eternity unless someone of the same blood as his orders it to do something else. Wano played a major role in this as they made these Poneglyphs. Wait…what do I mean by the same blood as his? How can Momonosuke order Zunisha? Something even Oden could not do?
And how do I know that Oden could not order Zou?
Because of what Pedro said here:
Momonosuke could order Zou because he is a distant progeny of the same family as Joy Boy not from Oden, but from Lady Toki.
Toki is a relative of Joy Boy’s, possibly a sister, or daughter etc. After the Ancient Kingdom fell, she escaped to Wano at Joy Boy’s behest possibly along with a few others.
**UNCERTAIN PART OF THE THEORY**
Kozuki Toki then used her power to go to the future, she kept traveling further and further each time for 800 years. Her main purpose was to ensure that knowledge of the Ancient Kingdom has been passed down properly. For 800 years she only saw the World Government getting stronger and knowledge of the Ancient Kingdom dwindling worldwide, that was until the Rocks pirates came to be. They were the first force against the World Government, and in their motives, Toki saw hope and decided to give her best to help her cause. She settled down with Oden to whom she revealed the existence of the Ancient Kingdom. She helped Oden and Roger reach Raftel who later found out the truth about the Ancient Kingdom. Just has things seemed to get better however, Kaido came to Wano seeking knowledge of the One Piece and killed Oden who refused to tell him.
And welcome to the present, where Momonosuke was sent 20 years ahead by his mother so he can take back Wano and subsequently revive the flames that would bring knowledge of the Ancient Kingdom to the world.
*Theory by ToBeThriller