Chapter 817 is titled "Raizo of the Mist".
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Jack and his men sail through the ocean, alive after their battle with the Marines. On Zou, Kin'emon shows the crest of the Kozuki Family on his back. However, Inuarashi and Nekomamushi start arguing again, but Momonosuke stops them, saying his father would be saddened to see this. Kin'emon reveals that Momonosuke is not his son, but is the son of Oden, the Daimyo of Kuri in Wano Country. Inuarashi and Nekomamushi reluctantly make peace in order to help him.
The Straw Hats are taken to the tail of the Whale Tree, where there is a hidden door leading to Raizo. They see Raizo chained to a Poneglyph, and are saddened by his ugly appearance, but become entranced when Raizo uses ninja arts.
On Zou, Kin'emon apologizes to the Mink Tribe as he removes his kimono, confirming his position by exposing a tattoo on his back. The minks recognize that Kin'emon bears the crest of the Kozuki Family like Raizo does, and the Straw Hats watch the interaction in surprise, having been under the impression that the minks would be hostile toward the samurai. Nami reveals that she heard that Inuarashi and Nekomamushi have the crests on their backs as well, meaning their bonds ran deeper than she originally thought. Kin'emon expresses his pleasure that the two rulers are alive, and they reciprocate the feeling, but immediately begin quarreling again despite their subjects' attempts to stop them.
Suddenly, Momonosuke cries out for them to stop fighting, wondering how they grew so bitter after being friends and telling them that he would not allow them to squabble, especially if the reason was his father. He says that his father would be saddened to see them like this, and Inuarashi and Nekomamushi lay prostrate before him and apologize. The Straw Hats wonder what Momonosuke meant when talking about his father, as Kin'emon is right there. The minks begin realizing in astonishment what Momonosuke must be if the rulers are bowing before him, and Kin'emon confirms that Momonosuke is indeed a lord. He tells the Straw Hats that he and Momonosuke are not father and son, but rather Momonosuke is the son of Lord Kozuki Oden, the daimyo of Kuri in Wano Country. The minks apologize for not recognizing Momonosuke as Kin'emon reveals that they pretended to be father and son in order to avoid drawing more attention to the young lord.
The Straw Hats react in surprise to Kin'emon's revelation, but Luffy does not care about Momonosuke's position. The two get into a fight, which annoys Kin'emon, but Kanjuro says to leave them be. Momonosuke then takes refuge in Nami's embrace, which enrages Kin'emon, but Nami is fine with it as she deduces that Momonosuke's father must be very wealthy, which annoyed Zoro and Usopp. Meanwhile, Inuarashi and Nekomamushi reluctantly decide to truce in order to avoid agitating Momonosuke, and the minks celebrate as the two grasp hands.
Later, Nekomamushi and Inuarashi take the Straw Hats, Law, and the samurai up the whale-shaped tree where Raizo is. The male pirates begin getting excited at the prospect of meeting a ninja, and imagine Raizo as a stereotypical hooded ninja. They reach a hidden entrance at the back of the whale's tail, and climb down a long set of stairs as they start hearing screams coming from inside. The excited Straw Hats reach the bottom, where they see Raizo chained to a red poneglyph. Raizo has a disproportionately large head and looks nothing like the ninja they thought of, causing them to be shocked and disappointed. Raizo shouts that he saw the heavy wounds on the minks that brought him food and asks why they did not turn him over to the enemy and if the country truly is safe now.
Raizo and the samurai are joyed as they reunite and Raizo is freed of his chains, and Robin notices the Kozuki Family crest on the wall as well as the red poneglyph. Robin wonders why it is red, and Inuarashi replies that it is apparently for a different purpose. He gives Robin permission to read it as the male pirates tell him to perform various ninja arts. Raizo wonders why pirates are obsessing over him, but Franky says that all men are obsessed with ninjas. Raizo shouts at the pirates to stop forcing their imaginations on him, as he does not perform some stereotypical ninja actions and is too ugly to do others. He says that ninjas are not performers, but as the Straw Hats gloomily turn away, he gives in and performs Smoke Release Jutsu, Clone Jutsu, and throws flower shurikens as he strikes a pose, which entrance the Straw Hats.
- Jack is shown to be alive after the fight with the Marines that escorted Doflamingo.
- As retainers of the Kozuki Family, Kin'emon, Raizo, Inuarashi, and Nekomamushi bear the family crest tattooed on their bodies.
- It is revealed that Kin'emon was only pretending to be Momonosuke's father. His real father is the master of the Kozuki Family named Kozuki Oden.
- Momonosuke is revealed to be the heir to the Kozuki Family and master to Kin'emon, Raizo, Kanjuro, Inuarashi, and Nekomamushi.
- The reason why Inuarashi and Nekomamushi started hating each other involves something that happened with Oden.
- Inuarashi and Nekomamushi reluctantly make a temporary peace with each other for the sake of Momonosuke.
- It is hinted Momonosuke and his father have the same ability as the late Gol D. Roger and Monkey D. Luffy.
- Another unknown character is stated to possess the same ability.
- Raizo is introduced and reunited with Kin'emon, Kanjuro, and Momonosuke.
- Zou is shown to retain possession of a poneglyph, which is colored crimson red.