Chapter 856 is titled "Liar".
The Sanji Retrieval Team in the Mirro-World manages to deduce Luffy and Sanji's location; Jinbe then brings up Pekoms, revealing that he rescued the latter from a plan set to occur at the wedding tomorrow.
In Sweet City, Bobbin is ambushed and shot by unknown assailants.
Inside their guest room in Whole Cake Chateau, the Vinsmoke Family celebrates the upcoming formalization of their alliance with the Big Mom Pirates. Outside their room, Big Mom's soldiers keep tabs on them to ensure they contact no one.
In the outskirts of Sweet City, Sanji gives Luffy his bento basket, which had been soiled during Sanji's journey. Luffy eats it and regains his strength, but Sanji tells him to leave, saying that he could not escape with him because he attacked his captain, the Baratie chefs remain his family's hostages, and he could not let his family be killed by Big Mom. However, Luffy punches him and forces him to confess that he truly wants to return to the crew, and Luffy offers his support in ruining the ceremony tomorrow.
In the Mirro-World, the Sanji Retrieval Team is unable to find Luffy and Sanji's whereabouts from the mirrors, and Nami deduces that they must not be in the castle, so she begins to think about the place they fought this morning. Chopper is bewildered to hear that the two fought, but Jinbe understands that Sanji must have had things he needed to do in his role as a member of the Vinsmoke Family and it would be difficult to get him to return. He then tells the team that they must hasten, as the wedding is actually not going to be a simple ceremony. He asks if they came with Pekoms, whom the team remembers and asks if he is all right. Jinbe affirms this, but says that the lion mink would have been killed as part of a certain plot had Jinbe not noticed it. In Sweet City, two citizens wonder if they just heard a gunshot, but are unable to tell in the rain. Meanwhile, an injured Bobbin curses three shadowed figures before collapsing.
In the sixth floor guestroom in the Whole Cake Chateau, the barmaids start passing out from the immense amounts of alcohol consumed, and Yonji calls them pathetic as he and his family continue consuming the "weak" alcohol by the barrel. He and Niji wish they had Nami to serve them, recalling of having heard that she was captured, before wondering if they can bargain to get her for themselves. Judge then advises giving the drinking a rest, saying that tomorrow night will be the time to party. He excitedly thinks about their upcoming alliance with the Big Mom Pirates tomorrow, and points out that their "failure", Sanji, helped this to come about. The laughing Vinsmoke men then have a toast to their "dud", reflecting that this is the first time he will ever be useful, unaware of the smiling Homies in the room who know of Big Mom's plan at the wedding. Later, the Chess Soldiers guard the Vinsmoke guestroom, receiving orders from Mont-d'Or to not let them contact a single person between now and the ceremony. The Chess Soldiers also guard Reiju who is still in the infirmary, and she remains awake as Judge and Big Mom fall sound asleep.
In the outskirts of Sweet City, Sanji approaches Luffy, who wakes up after smelling the bento basket in Sanji's arms. Sanji says he never told Luffy to wait there as he drops the bento basket at his feet, revealing the poor condition of the bento due to him dropping it and the rain getting into it. However, Luffy starts eating it and cries that it is extremely delicious, noting that Sanji put all the crew's favorite foods in it. However, Sanji calls him a liar. Finally, Luffy finishes the meal and fully regains his strength, and Sanji tells him to leave. Luffy is quickly taken aback and tells Sanji to come with him, but Sanji gives him the reasons why he is unfit to return to the crew. The first reason is that he attacked and disrespected Luffy, his captain, despite the latter coming to save him. The second reason is that Zeff is still being held as a hostage, and the third reason is that despite despising his family, he still does not have the conscience to let them be murdered tomorrow. Sanji asks if Luffy understands, but Luffy simply races up and slaps Sanji in the face, sending him crashing into King Baum's remains. Luffy then shouts at Sanji to tell the truth, and as he remembers all the times he spent cooking for the Straw Hats, Sanji tearfully confesses that he wants to return to the crew. However, he is powerless to stop the wedding and save his family, but Luffy assures him that they can work to wreck it together.
- The animals and living objects on the cover may be a reference to the Japanese fairy-tale "The Crab and the Monkey".
- Jinbe reveals that Pekoms is alive and tells something to the Sanji Retrieval Team about an ominous plot that will happen during the wedding ceremony.
- Bobbin is ambushed and shot by unknown assailants.
- Sanji gives his bento box to Luffy.
- Sanji resolves to help his family and Luffy decides to help him ruin the wedding ceremony.
- Judge is finally seen without his mask on, but his face is hidden by a shadow.