Chapter 849 is titled "Choniki in Mirrorland".
Cover Art Request: Brook composing music with tadpole notation P.N. Noda Skywalker from Osaka Prefecture.
The Vinsmoke Family, minus Reiju, talks about plans after the wedding, revealing their intention to make Sanji and Pudding live on Germa Kingdom in order to prevent Big Mom from taking advantage of them.
Meanwhile, Brûlée lowers Carrot into some boiling soup. However, unbeknownst to her, the Carrot hanging above the pot is actually a frog she accidentally used her mirror powers on. Carrot, who is in the attic, throws a rock at Randolph, allowing her to drop down and drop the pot of soup on Brûlée, defeating her. Carrot then defeats Randolph and some of Brûlée's henchmen, and Chopper frees himself and takes down the Noble Croc. Diesel attempts to escape and report to Big Mom, but Carrot defeats him, and she and Chopper take over the Mirro-World.
Meanwhile, Sanji prepares to cook food for Pudding. In the Room of Treasure, Brook defeats the remaining security, but Big Mom comes to the room in order to deal with Brook herself. In the Chateau courtyard, Pedro is surrounded by Big Mom's forces, and Tamago confronts him. Tamago reveals that Big Mom took away 50 years of Pedro's lifespan five years ago, causing Pedro to affirm that he did not intend to leave Totto Land alive.
Meanwhile, Reiju is left severely injured inside a hallway.
Inside the Vinsmoke Family's guest room, Yonji wonders where Reiju is before asking Judge where Sanji and Pudding will live after the marriage ceremony. Judge replies that they will live in Germa Kingdom in order to put Pudding under their power, as he believed that Big Mom, as a pirate, may try to take advantage of them afterwards. Niji wonders if Big Mom is planning the same tactic, but Ichiji reminds him that they do not care what happens to Sanji, causing Niji to laugh and look forward to living with his brother again.
Inside Brûlée's house in Mirro-World, Brûlée prepares to begin cooking Carrot in a soup, much to the delight of the various hungry people in her house. However, Chopper notes that Brûlée is basically digging her own grave, as the Carrot hanging over the soup pot is actually a frog that Brûlée transformed into Carrot using her powers. The real Carrot is in the attic, and she stands directly over the pot, crying for help to trick Brûlée's crowd and to mask the frog sounds her double is making. Chopper notes that of the 16 people in Brûlée's house, the most troublesome looking ones appear to be Brûlée herself, Randolph, the Noble Croc, and a mysterious man called Diesel. As Randolph prepares to cut the rope holding Carrot's double over the pot, Carrot throws a rock at him from the attic, successfully knocking him over. Brûlée is confused and angry at Randolph, and Diesel suddenly alerts her to an intruder in the attic. They then see Carrot hanging onto her double over the pot, and Carrot kicks the pot at Brûlée, sending the boiling liquid inside crashing down on her.
While the house falls into chaos, Chopper activates Brain Point and becomes small again, allowing him to free himself from his chains before eating a Rumble Ball. Randolph and several others race to help Brûlée, but Carrot creates a ball of electricity with Electro before slamming it into the ground, electrocuting all of them. Chopper then activates Monster Point right behind the Noble Croc, and as the Noble Croc looks around to find the source of the noise, Chopper grabs him by the tail and flips him over, sending him slamming backfirst into several of Brûlée's guests and knocking himself and them out. With Brûlée, Randolph, and the Noble Croc defeated, a shocked Diesel runs away in order to report this to Big Mom. He mocks Chopper and Carrot, saying they could not catch up to him, but Carrot easily catches up to him and bites him in the shoulder before covering his eyes, causing him to crash. Carrot and Chopper celebrate their victory over Brûlée's team, and prepare to travel through the island's mirrors in order to find their allies.
In Sanji's room, a servant reports to him that Luffy and Nami are currently imprisoned while Pedro and Brook are on a rampage. However, Sanji cuts him off and asks to have the food that he requested. Sanji prepares to cook some food for Pudding since she never ate lunch, and the servant understands, stating that she is still under the weather. In the Room of Treasure, Brook discovers the key to unlock the cage containing the poneglyphs, and one remaining security guard angrily attacks him, reprimanding him for causing such a mess. However, Brook cuts him and another guard down as he replies that that is good, as since Pedro is out risking his life for him he feels obligated to thoroughly succeed in his mission. As Brook enters the cage with the poneglyphs, Big Mom approaches Smoothie and the others outside of the Room of Treasure, telling her daughter to get out of the way. She then bursts through the door of the Room of Treasure and angrily confronts the terrified Brook, but she immediately takes an interest in his unique body. Meanwhile, Big Mom's forces chase Pedro into the Chateau courtyard, surrounding him. From the other side, Tamago greets his old acquaintance Pedro, the captain of the Nox Pirates, and wonders why he, who had craved life so much when he was here five years ago, was making the same mistake again. As Pedro removes his cap and Tamago removes his sunglasses, revealing that they both have injured left eyes, Tamago questions Pedro's decision to return in light of the fact that Big Mom took away 50 years of his lifespan five years ago, leaving him with little time to live. However, Pedro replies that he is aware of this, and that he has no intention to return to Zou alive.
Meanwhile, a heavily injured Reiju struggles to move down a hallway.
- The name of this chapter is a reference to the Japanese name of Lewis Carroll's famous novel, Through the Looking Glass (鏡の国のアリス Kagami no Kuni no Arisu).
- The Vinsmoke Family plans to take Pudding hostage after the wedding.
- Chopper and Carrot defeat Charlotte Brûlée and her team and take control of the Mirror World.
- Chopper is shown to be able to move after using "Monster Point".
- Brook defeats all the guards in the treasure room and begins to copy the poneglyphs, only for Big Mom to appear.
- Tamago herds Pedro into a trap in the courtyard where they meet again after five years. The last time they met, they left scars on each other's left eye.
- The name of Pedro's old pirate crew is revealed to be the Nox Pirates.
- Big Mom took 50 years of Pedro’s life when he was captured five years ago.
- Reiju has been badly injured.