Chapter 668 is titled "Pirate Alliance".
Luffy accepts Law's offer of an alliance to defeat one of the Four Emperors, despite the initial misgivings of the remaining Straw Hat Pirates. Law returns Franky and Chopper to their original bodies, leaving Nami to go into Sanji's body. The group establishes their current objectives: to discover a cure for the children, to find the samurai, and to kidnap Caesar Clown. The G-5 Marines battle the centaurs. In the burning lands, another group of centaurs releases a gigantic Slime creature on Caesar's orders, which quickly annihilates them all.
Nami is surprised by Law's proposal, calling it crazy and telling Luffy not to agree. Law tells him that it will not be immediate, and following the plan will only give them a chance at defeating one of them. Luffy asks which Emperor Law had in mind, and Law tells him the answer which was only audible to Luffy and Nami. Luffy, satisfied with Law's answer, agrees to the alliance, much to Nami's surprise. Back at the remains of the first two research labs, Luffy tells the other Straw Hat Pirates present about his plan, and they are just as surprised. Usopp starts shaking Luffy and yelling at him for being so reckless, Nami tells him they need to follow their own pace in the New World. Chopper agrees, saying it is too early to fight an Emperor. Nico Robin tells Luffy she will follow his decision, but betrayal is always an aftereffect of any pirate alliance, and his tendency to trust people too quickly could be a problem. Luffy asks Law if he is going to betray him, Law answers no. Luffy tells his crew not to worry, since they are with him. He thinks Law is a good person, but if something does go wrong, they've all trained for two years and can handle it. The Straw Hats are both shocked and humbled by their captain's words.
Law uses Shambles, returning the displaced crew members to their normal bodies. Franky is happy to be back in his own body, and Robin is glad to have him out of Chopper's body. Chopper is glad to be back, but angrily asks why he is so beaten up. Franky and Luffy both apologize and blame the other for the damage to Chopper's body. Luffy blames Franky for going on a rampage and having to be subdued while Franky blames Luffy for using excessive force to bring him down. Chopper says they are both to blame and both apologize. The only one unhappy with the outcome is Nami, who was placed in Sanji's body, due to her body not being there. Luffy, Usopp, and Chopper, on the other hand, find her predicament hysterical. Nami yells at Law to do something about it, but he says he cannot without another body. He then turns his attention on the sleeping children, whom Luffy says he wants to save. Law tells them about their drug addiction, but Chopper tells him they know already. He explains how they want to send the kids home, but cleansing their bodies will take a while, and their size is an issue. Law explains that human growth projects is something the World Government has been working on for hundreds of years as a method of creating an army of super soldiers. Law adds that Caesar Clown is probably trying to perfect them and get the better of Vegapunk and the World Government. He asks if they really want to save the kids. Nami replies they do, saying they cried and begged for the crew's help, saying even the kids know something is up. Nami states she will not leave the island until the kids are safe. Law takes that to mean she will stay here alone, but Luffy corrects him, saying that he does not leave people behind, so if Nami and Chopper stay, everyone is staying. He then adds that Sanji wanted to put the samurai back together, and asks Law for his help since he is their ally now.
Usopp clarifies for Law, saying the two captains have different ideas of what it means to have an alliance. Luffy states it is like being friends. Usopp goes on to mention Luffy's stubbornness. Law states that Luffy's crew's wishes have nothing to do with their agreement. He then gives in, saying they do not have time for it. He tells the Straw Hats to take care of the samurai. He then asks who their doctor is, saying the two of them will check out the drugs given to the children as well as find a way to keep Caesar busy. Chopper apologizes for his immobility as Usopp ties him to Law's head, mortifying the captain and causing the rest of the Straw Hats to laugh uncontrollably. Law, having relocated Chopper from being tied to his head to dangling from the tassels of his sheath by one horn, goes on to say that the Straw Hats are on Caesar's hit list, and he will not stop until they are dead. He tells them about Caesar's bounty and how he got it, as well as a break down of his abilities and weapons. He also adds that if Caesar were to lose his perfect little hideaway, he would come after them with everything he could. He adds that anyone who cannot use Haki cannot go near him. Luffy tells Law that the four Haki users on the island are the two of them, as well as Zoro and Sanji. Luffy confirms for himself that all Law has to do is kidnap the mad scientist. He asks who they will get the ransom money from. Law says the kidnapping is less about money and more about causing a little chaos. He tells them to focus on capturing Caesar, and then he will explain the plan in detail to them. He gives them one last chance to opt out, but Luffy holds firm to teaming up. Law reminds him to relay this information to his absent crew members.
Back outside the lab, the G-5 Marines are under attack by the centaurs. Several of the attacking centaurs are identified as former prisoners. Smoker asks how the incident report from four years ago could state that there were zero survivors. Monet informs Caesar that a Den Den Mushi rings inside the lab but he says to ignore it, saying he knows who it is and what they will say. A report saying they opened the door, something came out, how it got the others, and they need help. Caesar then comments on how rare it is to have so many guests at once. He then says he will introduce his pet, adding that not one of them will make it off the island alive.
On the burning side of the island, one of the centaurs is trying to radio in to Caesar, just as expected earlier. The two centaurs panic, wondering what they just released. They are being chased by a formless blob. As they run, they get hit by some gas and suffocate. The blob then absorbs them. The blob is then introduced as the creature Slime.
- Edward Newgate and Portgas D. Ace's graves are shown for the second time. The cover story "From the Decks of the World" ends.
- Three sake cups, as well as the bottle of sake next to them are shown on the wooden box in front of the graves. These are later revealed to have been left by an old friend.
- An alliance is formed between the Straw Hat Pirates and the Heart Pirates, with the intention of taking out one of the Four Emperors.
- Chopper and Franky return to their original bodies, while Nami is placed in Sanji's body.
- Law reveals that the World Government have been researching how to turn humans into giants and that is what Caesar Clown has been doing to the kidnapped children.
- Law and Chopper head off to find medicine for the kids.
- Law, Zoro, and Sanji are confirmed to possess Haki.
- Law and the Straw Hats form a plan to capture Caesar Clown.
- Caesar's minions engage the G-5 Marines.
- Caesar has unleashed his pet creature, a giant Slime monster.
- first introduction
|Punk Hazard Arc|
|From the Decks of the World|
|Manga Chapters (covers)|