Chapter 878 is titled "Mink Tribe, Guardians Captain Pedro".
Five years ago, after having most of his lifespan taken away, Pedro revealed that his crew was named the Nox Pirates because the night came just before the dawn; as a child, he had wanted to sail with Gol D. Roger, but Roger said his time was limited and Pedro's time would come later. In the present, Pedro's explosion causes Perospero's candy bindings on the Straw Hats to disappear, and the Straw Hats prepare to escape with Coup de Burst. A distraught Carrot attacks Katakuri but is overpowered, Big Mom begins eating the Sunny, and Perospero is revealed to have survived the explosion. Luffy steps in to fight Katakuri, and says that he will meet everyone else later as he grabs onto Brûlée and pulls himself and Katakuri into the Mirro-World. The rest of the group on the Sunny then activate Coup de Burst and fly over the Big Mom Pirates' blockade. In the Mirro-World, Luffy and Katakuri prepare to battle.
Five years ago after Big Mom agreed to remove 50 years of Pedro's lifespan, Pedro was escorted out of Totto Land on Perospero's ship. Perospero was impressed by Pedro's resolve in his confrontation with Big Mom, but noted that the 27-year old mink was now effectively 77 and would not have much longer to live. Pedro replied that at least he could now choose the way he died, and Perospero poked fun at his crew's name of Nox Pirates, given that Nox means night. However, Pedro responded that the night is what gives way to the dawn, as he remembered asking Gol D. Roger and Kozuki Oden to sail with them when he was a child. Roger told him to remain on standby, as his time was limited and the time for Pedro's turn would come later. Much later, when Pedro was training, Wanda told him that Roger had died. Taking Roger's words to heart, Pedro made it his goal in life to become the foundation of the Dawn of the World which the Straw Hats would bring.
In the present, Luffy yells out in shock and Carrot breaks down in tears as Pedro unleashes a suicidal explosion to take out Perospero, and Katakuri is shocked at the blow dealt against his older brother. The candy encasement on Chopper, Brook, and the Thousand Sunny melts away, freeing the Straw Hats, and Big Mom is blown away by the force of the explosion. A distraught Carrot tries running toward the scene of the explosion, but Nami holds her back, reminding her that Pedro's sacrifice saved their lives. Luffy orders everyone to set sail, saying that if they wasted their chance to escape, they would not be able to face Pedro. With Nami's help, Jinbe prepares to activate the Coup de Burst to fly them northwest, but Katakuri states that they are getting too worked up as he prepares to attack and the tarte ships surrounding the Sunny prepare to fire. Carrot rushes toward Katakuri, remembering how Pedro told Shishilian she would not be suited for the sword when she was training in it during her younger days, much to Shishilian's anger. Later, Pedro gave Carrot her signature gauntlets, telling her to prepare for the time when it is her turn.
In the present, Carrot attacks Katakuri, but the Sweet Commander easily subdues her with a stomp as he races toward Luffy. Luffy then attacks Katakuri and declares that the Sunny will set sail under his watch, and attacks Katakuri with Elephant Gun. Despite Katakuri trying to block it with mochi, Luffy manages to grab ahold of him, and Katakuri foresees what Luffy is going to do, which will prevent him from attacking anyone else. Luffy replies that Katakuri will be unable to prevent what he foresees, but things quickly take a turn for the worse as the tarte ships fire cannonball homies at the Sunny, Big Mom starts taking bites out of the ship's stern, and Perospero emerges from the explosion heavily injured but still alive. Luffy calls out to his teammates and says he will leave the rest to them as he grabs onto Brûlée, who is standing inside a mirror nearby, and pulls himself and Katakuri into the mirror. With the cannonballs converging on them, the Sanji Retrieval Team activates Coup de Burst, unleashing massive explosive power into Big Mom as they fly above and away from the Big Mom Pirates' blockade. Amande reports that the Sunny has escaped, and inside the Mirro-World, Luffy stands against Katakuri. The Sweet Commander remarks that Luffy did a good job, and Luffy shatters the mirror leading to the Sunny as he and Katakuri prepare to have a real one-on-one fight.
- Pedro and Wanda are shown as children.
- Perospero survived the explosion but is grievously injured, causing him to release his entrapment of Chopper, Brook, and the Thousand Sunny.
- Luffy takes Katakuri into the Mirro-World to continue fighting him there.
- Luffy destroys the mirror leading back to the Thousand Sunny.
- The Thousand Sunny escapes from Whole Cake Island and is heading toward Cacao Island.