Chapter 1020 is titled "Robin vs. Black Maria".
On the Skull Dome roof, Kaidou insists that Yamato's Devil Fruit, the Inu Inu no Mi, Model: Okuchi no Makami, be used to rule over Wano Country and keep it guarded. However, Yamato refuses and promises to liberate Wano's populace to the outside world as the two of them clash with elemental breath attacks.
Meanwhile, Black Maria tries attacking Robin and Brook with an "illusion mist" which causes illusions of those they love to appear; however, the duo quickly see through and attack them. As Brook takes down Maria's living weapon Wanyudo and confronts the rest of her subordinates, Maria derides Sanji and the rest of the Straw Hats' seeming weakness for making Robin face her. However, Robin swiftly rejects this claim as she generates a giant clone of herself to confront Maria.
On the Wano mainland, Momonosuke and Shinobu have found Luffy, who is conscious and alert after having eaten meat. Needing to get back to Onigashima and finish off Kaidou, Luffy asks Momonosuke to fly him up there.
Atop the Skull Dome's roof, Kaidou tells Yamato that the Devil Fruit the latter once ate from—the Inu Inu no Mi, Model: Okuchi no Makami—is a very valuable Mythical Zoan fruit, and that it was a mistake to let Yamato, someone claiming to be Oden, gain its power because the "Okuchi no Makami" is Wano's "Guardian Deity". Kaidou states that, thus, Yamato ought to protect Wano for him, which the latter refuses, but Kaidou simply says that Orochi had a talent for exploitation, and seeing how his actions turned Wano into such a great weapons factory, all they have to do is take control and keep it running. Yamato, however, says that he plans on helping to protect the country from Kaidou and to open it up, before unleashing a blast of some kind from his mouth called Namuji Hyoga, which Kaidou counters with his Bolo Breath, before saying that he will not let that happen.
In the Third Floor's Banquet Hall, Nico Robin is approached by what appears to be her departed loved ones: her mother Nico Olvia, her mentor Professor Clover, and Jaguar D. Saul. The three tell her to approach them and Robin starts to do so with her arms open. Brook, however, tries to tell her over and over not to go to them, and sure enough, she stops and admits the enemy is trying to fool her, using Tres Mano: Freesia to strike the fakes and expose them as Black Maria's subordinates: SMILE eaters Nure-Onna and Tenjo-Sagari, and female Number Kunyun, who had been disguised by Black Maria's Illusion Mist. As Brook and Robin then run from Black Maria and her lackeys through a hallway, Brook tells Robin that she should have given him a sign that she was not affected by their trick. Robin notes how Brook was unaffected as well, who explains that it was because he was adrift in the Florian Triangle for fifty years and would dream about his deceased crew being alive, so he became used to being hurt by illusions. Robin offhandedly remarks how similar the two of them are due to all their past trauma, just as Black Maria uses Furisode Wanyudo to strike at them, but misses. Her weapon, the staff whose head portion is a flaming wanyudo, is revealed to be another SMILE user aptly named Wanyudo, a man who ate a pug SMILE and is keeping the staff's fire lit by running around in its wheel like a hamster.
Black Maria jumps onto the ceiling, using her spider silk to keep herself suspended upside-down, and declares that her foes are clearly dreaming if they think that they could beat Kaidou. The two Straw Hats dodge Black Maria's staff-whirling attack, which sets the floor ablaze. Robin uses Spider Net to keep herself, and Brook, hanging from the ceiling as well, exclaiming how Black Maria will burn down the whole castle if she continues like that. Black Maria sarcastically thanks her for her worry and notes how, perhaps, Robin ought to just surrender and let herself get caught. Brook, though, uses a move called Cold Soul to freeze the Wanyudo, eliminating the fires. Infuriated, Black Maria swings at Robin, causing her to let go of the ceiling. As she falls, Black Maria insults Robin by saying that, deep down, she knows the Straw Hats will sell her out, while Brook freezes the fire on the ground using Soul Parade so Robin may land safely.
Black Maria says that Sanji knew she was hunting Robin and yet still called the latter to their location, arguing that Robin is simply baggage to her friends due to the powerful figures that are after her. She adds that, with Sanji now the laughing stock of Onigashima, yet having the Straw Hats' number-two bounty, their crew must truly be low-level. Robin and Brook are unfazed by Black Maria's insults, and Brook simply asks Robin if she would like to take care of Black Maria by herself from this point on, which Robin confirms, leaving Black Maria's subordinates to Brook. Robin tells Black Maria that her insults mean nothing because she knows how kind Sanji is, and Black Maria would never understand what it means for him to rely upon Robin. Calling Sanji one of the "Pirate King's Two Wings" that will allow him to soar, Robin then shows off a new technique, Gigante Fleur, to create a giant, multi-armed clone of herself behind her.
Down at Udon's Tokage Port, Momonosuke and Shinobu have reunited with Luffy and the Heart Pirates, who have given Luffy all of their food, yet he still demands more meat. Momonosuke is relieved to see Luffy alive but starts crying over what happened with Kin'emon and Kikunojo, but Luffy tells him to not cry yet until Kaidou is beaten. Off in the distance, Caribou watches Luffy with the others and demands Luffy get himself together or he (Caribou) will never be able to escape Wano. Luffy then points up into the air, at the floating Onigashima, and tells Momonosuke that he needs him to help take him back up to the island, by transforming into a dragon and flying him up there.
- Yamato continues to battle against Kaidou.
- Black Maria's battle with Robin and Brook is shown.
- With the assistance of illusionary mist created by Black Maria, her subordinates disguise themselves as people from Robin's past: her mother Olvia, her mentor Clover, and her friend Saul.
- Black Maria's weapon is revealed to be operated by Wanyudo, a pug SMILE user.
- Robin faces Black Maria alone while Brook faces her subordinates.
- Robin uses a new technique, Gigante Fleur, to create a massive clone of herself with many arms.
- Luffy and the Heart Pirates reach the shore and are reunited with Momonosuke and Shinobu at Tokage Port.