Chapter 842 is titled "The Power of Fullness".
In the Germa Kingdom, Reiju heals Sanji's face with an electric mask. She then asks where he got his sense of chivalry from, and Sanji reveals that Zeff instituted it into him. Sanji and his family then depart to meet the Charlotte Family at the Whole Cake Chateau.
Back at the Seducing Woods, Cracker attempts to finish the battle, but Luffy activates a new form of Gear Fourth known as Tankman, which makes his obese body even larger. Cracker is absorbed into Luffy's body and then shot into the distance.
Cracker creates more Biscuit Soldiers to battle Luffy, and he tells King Baum that he will report the tree homie's insubordination to Big Mom. Baum replies that none of them can put up a fight against Nami due to the power of the Vivre Card she carries, but Cracker is not swayed by the excuse and tells him to save it for Big Mom. Cracker then complains that Nami keeps producing rain that softens his Biscuit Soldiers, making them edible. However, Nami berates Cracker for complaining about a pirate's fight, telling him not to lash out at her soldiers. The homies are appalled to be called Nami's soldiers, but fall right in line to her when she pulls out the Vivre Card. Cracker prepares to finish the battle by sending more Biscuit Soldiers at Luffy, and Luffy prepares to eat all of them despite his stomach barely being able to handle it, causing him to wonder if he can stop them without eating them. Nami orders her homies to protect her as she releases a Weather Egg, and she tells Cracker that even though he is a Yonko Commander, Luffy is the man who will become Pirate King and his stomach is limitless. An exhausted Luffy contests Nami's last point, and Nami sends rain pouring down on the Biscuit Soldiers. Luffy reluctantly eats more of them as he remains intent on seeing Sanji.
Meanwhile at Sweet City, people are talking in shock about things they are seeing in their mirrors. As a woman applies lipstick in front of a mirror, she accidentally runs the lipstick across her face when she sees Chopper and Carrot running inside her mirror. Inside Charlotte Brûlée's mirror world, Brûlée chases Chopper and Carrot with a scythe, and the two start to run out of energy.
In the Germa Kingdom, an aide reports to Judge that preparations are ready and now it is time to head for the Whole Cake Chateau. Meanwhile, Reiju puts a gelatinous mask on Sanji, saying it will sting for a bit. Sanji then receives a large shock from the mask, putting him in pain, but his swollen face is returned to normal. Reiju says that his face is still injured, but his current state will still be better for his meeting with Purin. Even though Purin's last name will not change upon marriage, Sanji will still be able to live a happy life with her if she likes him. Sanji gets angry, but Reiju reminds him that it was his choice to come back and that this was the extent of the help she would give him. Reiju then asks where Sanji got his chivalry from, and Sanji remembers back to his childhood on the Baratie. He and the other cooks were disappointed that Zeff refused to hire a female cook, and Zeff stated that he trained all of them through kicks, so he did not want to subject a woman to that. Sanji asked why Zeff would not just treat her like them, but an angry Zeff kicked him and shouted that men are not meant to kick women. Zeff said that he did not care how many times Sanji messed up as a human being, but if he messed up as a man, he was better off losing his manhood. Sanji wondered why Zeff would go that far, but Zeff replied that it was his duty as Sanji's parent, shocking Sanji. In response to Reiju's question, Sanji answers that he is just following the old laws of the universe. Sanji is then brought out to go to the Whole Cake Chateau for the gift exchange with Big Mom, and the Germa 66 soldiers cheer Sanji on as the Vinsmoke Family boards a carriage pulled by a large cat. Sanji sits in sullen silence in the back of the carriage between Niji and Yonji.
In the Seducing Woods, Luffy tells Cracker to give his Biscuit Soldiers a rest, saying that he could not eat anymore. Cracker is gleeful that Luffy has reached his limit, although Luffy is not willing to throw up the biscuits he ate. Cracker then rushes toward Luffy as he offers to help him by stabbing holes in his stomach and end the battle, but Luffy blows air into his muscles again. He expands even more as he reveals a new form of Gear Fourth: Tankman. Cracker is bemused by Luffy's new form and asks if he can even move. Cracker tries to stab Luffy with Pretzel, but the sword is absorbed into Luffy's body, confusing him. Cracker is then absorbed into Luffy's body, and Luffy tells Nami not to spray any water on the remaining Biscuit Soldiers. Luffy then pushes Cracker out of his body and sends him flying through the Biscuit Soldiers and into the distance, injuring the Sweet Commander.
- A flashback where Sanji learns his chivalry from Zeff is shown.
- The Vinsmoke Family departs for Big Mom's castle.
- It is revealed that the Bisu Bisu no Mi's biscuits weaken when soaked.
- Luffy uses another variation form with Gear Fourth, called Tankman: Full Version, and deals a massive blow against Cracker.
- There is an error with Luffy missing his scar on his chest during the whole chapter.