Chapter 855 is titled "Gugyurururu!!!"
Inside the Mirro-World, Nami, Chopper, Carrot, Pedro and Jinbe locate Brook, who is still being held by a sleeping Big Mom. The group hatches a plan to silently switch Brook with an identical corpse. After a few tries, they manage to wake Brook and make the switch. Brook then reveals that he succeeded in stealing rubbings of Big Mom's poneglyphs, having stored them inside his skull.
After arriving at the promised location, Sanji begins to search for Luffy. Hearing a loud growl, he follows the sound and spots his captain, weak and asleep from hunger at the base of the defeated Kingbaum.
After hearing the commotion caused by Sanji's attack, some of Bobbin's subordinates race toward his location. However, Bobbin bounces his head around, causing them to fall asleep. He tells them that there is nothing to worry about and that he will deal with the situation himself, before breaking off into a sprint as he says that even demons come to Big Mom's tea parties.
Inside the Mirro-World, Nami, Chopper, Carrot, Pedro and Jinbe locate a mirror inside Big Mom's bedroom. After spotting her asleep, with a snoozing Brook in her hands and Zeus, Prometheus, and Napoleon asleep around her, the team ponder how to rescue Brook. Brûlée screams out for Big Mom to save her, causing the team to bind and gag her and Diesel, but Big Mom does not notice. Instead, half-asleep, she only notices a fly buzzing around her room, and smacks the fly into the ground with extreme force before falling back asleep. The noise wakes Brook, but he goes back to sleep when he sees that it was just a fly. Zeus, Prometheus, and Napoleon also wake, and, believing that Big Mom was being attacked, attack the spot where she had smacked the fly before also returning to sleep. The Sanji Retrieval Team is terrified at what they just witnessed, wondering how they are supposed to save Brook.
Meanwhile, Sanji runs through Sweet City, on his way to the place where Luffy promised to be waiting for him. On the way, a dog races up to him and tries to get into his basket of food. Sanji shakes the dog off, telling it that the food was not for it.
Back inside the Mirro-World, the team finds a skeleton in the Chateau's Execution Room and some seaweed in the kitchen, which they use to make a stand-in for Brook. Jinbe puts Brûlée directly in the mirror, to allow any of them to cross through it. Chopper sneaks into the room, but accidentally sneezes, causing Big Mom to semi-consciously slam her hand down where he is standing. Carrot tries next, quietly landing on Big Mom before whispering to Brook to wake up. However, she is forced to flee from a sleep bubble coming from Big Mom's nose, and Zeus spots her. Thinking she is the fly, Zeus shoots a lightning bolt at Carrot. Pedro is the next to try, but Big Mom starts tossing and turning, forcing him to retreat. However, Big Mom finally lets go of Brook, and Nami sets out to retrieve him. Nami wakes Brook up, but Brook screams at the sight of the skeleton she is holding. Thinking the noise is still coming from the fly, Big Mom grabs Prometheus and throws it at the two Straw Hats, but Jinbe manages to bring them safely back to the Mirro-World.
Sanji reaches the outskirts of Sweet City, where he comes across the bodies of the soldiers that Luffy and Nami had earlier fought. He begins to search among them, looking for Luffy.
Inside the Mirro-World, Brook expresses his shock at his sudden rescue, and Nami gets mad at him for screaming and almost getting them killed. Pedro then apologizes to Brook for putting him in danger by sending him to a highly guarded room, but Brook replies that it was a once-in-a-lifetime chance, as they would be unlikely to succeed in reaching the poneglyphs again without fighting a full-scale war. He then pulls out rubbings of Big Mom's three Poneglyphs from inside his skull, explaining that he had barely managed to finish copying them before Big Mom arrived. The others, including Brûlée and Diesel, are shocked that he actually succeeded in copying the poneglyphs. The team celebrates Brook's accomplishment, and Chopper declares that they have only one objective remaining: to retrieve Sanji.
Finally, after a period of searching, Sanji hears the sound of a stomach growling behind him. After following the sound, he smiles tearfully as he sees Luffy leaning against the base of Kingbaum, asleep and weakened from hunger.
- Bobbin’s bounty is 105,500,000.
- Bobbin decides to go after Sanji himself.
- Bobbin has an ability to put people to sleep.
- Nami, Chopper, and Carrot see Big Mom in person.
- It is shown that Napoleon can turn into a sword.
- Chopper’s group rescues Brook from Big Mom’s clutches.
- Brook reveals that he has succeeded in getting the copies of the three poneglyphs and hid them inside his skull.
- Sanji arrives at the place where Luffy promised to wait for him.