Chapter 821 is titled "Understood".
Jack and his men attack Zunisha's left front leg as Luffy and Momonosuke hear Zunisha telling them to command it. Momonosuke realizes that Jack is attacking Zunisha, and the minks prepare to head to sea to combat him. Momonosuke finds out that a long time ago, Zunisha was punished and not allowed to do anything except walking, and he can give it permission to fight. He does so, and Zunisha smashes Jack's fleet to pieces with its trunk.
The ground shakes and houses begin to collapse. People run to avoid being crushed as Inuarashi commands everyone to keep away from the buildings and hold tightly to the trees. Nekomamushi realizes that something is wrong with Zunisha. Luffy and Momonosuke are plagued by a voice calling out to them that only they can hear. Luffy doesn't understand why no one else can hear this voice and proceeds to asks the voice who it is as it tells him to hurry.
Jack, who is bombarding Zunisha with cannon fire from the water, orders his men to keep hitting the same spot on the elephant's left front leg. The crew cheers when they see their attacks have an effect, and Jack proclaims that even a regular elephant will stampede at the sight of a lone bee. Jack assumes that due to Zunisha's advanced age, its skin would be much weaker now. Jack calls the elephant an old relic as the cannons keep firing, their objective being to bring the elephant to its knees to allow easier access to its head. At which point they would kill it in what everway they see fit.
Zunisha begs whoever can hear its voice to issue a command. Luffy cries out in frustrated confusion, demanding to know who is telling him this as well as what it means. Nami asks Luffy at whom he is yelling, since no one else can hear any voice. An annoyed Luffy declares that all he can do is hear the voice, for its unknown owner does not listen. Pedro recalls that Gol D. Roger and Kozuki Oden said the same things as Luffy when they visited Zou. They could only hear but not converse with a disembodied voice. Momonosuke then has a vision, and sees Jack attacking Zunisha. He quickly tells everyone what he saw as well as their location and numbers. Everyone is surprised by Momonosuke's declaration as well as the fact that Jack survived his skirmish with the Marines. Kin'emon asks how Momonosuke knew this, and the frightened child simply says they came into his head.
Zunisha warns everyone of the danger they would be in if the pain from the attack caused it to fall. Inuarashi orders the country's ships be deployed, with the intent to fight Jack at sea. Momonosuke then realizes that the voice he is hearing is Zunisha's. He begins relaying the story Zunisha tells him. Long ago, Zunisha committed a crime. As punishment, it was not allowed to do anything except walking and could only act when given an order. Zunisha is now asking for an order, an order to fight the attacking enemy. Luffy tells Momonosuke to give the order, saying if he doesn't, they will all end up at the bottom of the sea, telling him to scream as loud as he can. Momonosuke tells Zunisha not to give up, and gives the order to retaliate against Jack. And so, with a single swing of its trunk, Zunisha annihilates the attacking ships. The ships are knocked to splinters and crash into the sea as the crew is sent flying.
From his lookout, Bariete observed the fleet's complete annihilation. After a few moments, the mood returns to calm as people try to figure out what happened to the attacking fleet as Momonosuke observes that he can no longer hear the voice. Bariete then relays what he saw through his telescope to the rest of the village. Inuarashi is stunned by the fact that Zunisha possessed a will of its own. With Momonosuke asleep on Robin's lap, Kin'emon takes the opportunity to ask if Oden knew about his son's ability to hear voices. Luffy breaks the stillness by asking why everyone seemed down. Nekomamushi decides they need to figure out how Jack was able to find Zou, otherwise the people could be susceptible to another attack. Luffy gives him some encouragement and points out how great it is to have the elephant on their side. Luffy then declares they are leaving and asks for lots of food.
On an island in the New World, a Den Den Mushi rings. When it is answered, Scratchmen Apoo informs Kaido that communication with Jack is no longer available.
- Zunisha's shaking is revealed to be the result of the Beasts Pirates' attack.
- Both Kozuki Momonosuke and Monkey D. Luffy are capable of hearing Zunisha's voice, but Zunisha will only respond to Momonosuke. Pedro claims that both Kozuki Oden and Gol D. Roger experienced that difficulty.
- Momonosuke is also able to share Zunisha's eyesight.
- Zunisha's past is somewhat revealed: it committed a crime and is not allowed to do anything except walking and was sentenced to follow orders, only ceasing its endless march when ordered otherwise.
- Under Momonosuke's order, Zunisha defeats Jack and sinks his fleet.
- Inuarashi was unaware that Zunisha possessed a personality and will.
- Luffy prepares to disembark from Zou.
- Scratchmen Apoo seems to be working with Kaido, and was in contact with Jack.