Chapter 857 is titled "Rook".
The Sanji Retrieval Team finds Sanji and Luffy from mirror shards on the outskirts of Sweet City, and Luffy and Sanji tell them about their intention to crash the wedding and save Sanji's family. Knowing that they are vastly outnumbered by Big Mom's forces, Jinbe asks Luffy about proposing an alliance to Capone Bege, who also seeks to bring down Big Mom in order to destabilize the world's structure of power. Pekoms had been shot by Bege after being offered to work with the latter but refusing, though had been saved by one of Jinbe's comrades. Despite Bege's actions, Luffy reluctantly agrees to work towards a deal. Inside his crew's hideout, Bege learns of his upcoming meeting with Luffy and is willing to work with his fellow Supernova, though will not hesitate to take Luffy down if the latter angers him.
Sanji is surprised to hear that Jinbe rebelled against Big Mom and freed Luffy and Nami, and is grateful that Nami is safe. He solemnly reflects that he cannot bring himself to face Nami after all the grief he caused his crewmates. He and Luffy then notice that the rain is stopping. Inside Mirro-World, the Sanji Retrieval Team discovers Luffy and Sanji from a mirror shard that Nami had while she and Luffy were riding on Kingbaum, so they look for more shards nearby. Luffy hears Chopper's voice calling out from the shard, and explains to an appalled and confused Sanji that the rest of their crewmates are inside the mirrors. Luffy talks to his teammates, and they tell him that all of them have been rescued and that Brook managed to get copies of the poneglyphs. Pedro then asks if Luffy and Sanji reached an agreement, and Luffy replies that Sanji is not coming back yet, shocking everyone. Luffy reveals that they are going to crash the wedding and save Sanji's family, after which Sanji will come back to the crew. The Sanji Retrieval Team falls into a stunned silence, and Sanji states that he cannot drag his crewmates into a battle with a Yonko. However, the Sanji Retrieval Team immediately erupts with affirmation, expressing their joy at the possibility of getting Sanji back. Nami coldly states that she will never forgive Sanji for putting her through such fear the previous day, but then says that she will forget about it in order to crash the Tea Party and get him to return, which puts Sanji into a euphoric state.
Jinbe then says that he knows what they have to do, as Big Mom's investment into her tea parties would guarantee her unbridled wrath against them. Not only that, but the ministers they had faced were only a small fraction of the Big Mom Pirates, who would have many powerful people attending the tea party. This is in addition to the various rulers of the Underworld that have been invited from all over the world. In contrast, their team consists of ten people. Brûlée and Diesel react in outrage that they were numbered among the team, telling the Sanji Retrieval Team to drop dead. Jinbe then asks if Luffy knows Capone Bege, which Luffy affirms, and Jinbe reveals that Bege is a boss of one of the five most powerful mafias in the West Blue. Jinbe had heard that Bege was a person who cut off animal heads and watched in joy as their lifeless bodies writhed around. The same applied to other organizations, as Bege would go directly after the boss. However, he only took his opponents' wealth; rather than gain power from taking them down, he took pleasure in watching the power struggles that formed as a result. Because of this, Bege is targeted by many enemies, but he enjoys that too as he has managed to dispatch them with his Devil Fruit powers. These habits did not change as Bege grew tired of his land exploits and set off to sea as a pirate, as he took down many captains of famous pirate crews. Now, he is protected from his enemies by Big Mom, and due to his sharp vigilance and high defensive powers, he acquired the title of "Rook" and was placed in charge of security at the wedding. Thus, since his crew is the security, there is nothing standing between them and Big Mom. As Big Mom plans to murder the Vinsmoke Family during the wedding ceremony to take control of Germa 66, Bege plans to take the head of Big Mom herself.
The Sanji Retrieval Team is bewildered to hear about this and all the schemes taking place during it. Jinbe then reveals that Pekoms was taken by Bege and was offered to help in the plan, but the steadfastly loyal lion mink refused. Bege then shot him into shark-infested waters in order to prevent him from revealing the plan, but Jinbe's crew found him and rescued him just in time. Luffy is angered that Bege would do such a thing, but Jinbe states that it may be wise to not consider Bege an enemy despite what happened to Pekoms. Rather than having the Sanji Retrieval Team quickly come up with a plan for the wedding in five hours' time, Jinbe suggests that Luffy ally with Bege, who has been meticulously planning for the event. Luffy then agreed, despite the ensuing protests of his teammates, and Jinbe states that he has already made the preparations, saying that they could always decline the alliance if Luffy ultimately disagreed. In the Fire Tank Pirates' base in northwest Whole Cake Island, Vito affirms that he disposed of Bobbin to prevent him from going after his hero Sanji. Someone asks Bege if Jinbe's group is really coming here, and Bege affirms this, saying that Jinbe does not joke around and it is in both of their interests to oppose Big Mom together. The rest of their dealings will depend on how Luffy acts, with Bege being willing to dispose of his fellow Supernova if Luffy makes him angry.
- Chopper's group contacts Luffy and Sanji through a mirror shard.
- Powerful members of the Big Mom Pirates besides the ministers will be attending the wedding.
- Various people with connections to the Underworld were invited to the wedding.
- Bege is revealed to be one of five bosses who control the underworld society in the West Blue.
- It is revealed that Bege was plotting against Big Mom.
- Bege offered Pekoms to join in on the plan, but Pekoms refused and was then shot and sent into shark infested waters to keep him silent.
- Pekoms was saved by Jinbe's crew and is currently recuperating.
- Jinbe proposes that Luffy and Sanji form an alliance with Bege and Luffy agrees to meet him, despite the majority of the Sanji Retrieval Team being against the idea.
- It is revealed that Vito was the one who attacked Bobbin.