One Piece's Reverie arc has shown a whole new side of Eiichiro Oda's world as fans have seen many fan-favorite allies and foes in a whole new light. With Luffy getting a major promotion in title and bounty, his status as the "Fifth" Emperor has certainly gotten a lot of attention from the wrong kinds of people. This includes Kaido and Big Mom, who begin plotting Luffy's death in the latest episode of the series in an ominous return for the duo.
In Episode 887 of the series, fans see Kaido re-appear in full before his big run through the upcoming Wano arc and he's holding quite a grudge against Luffy and the Straw Hats for destroying the SMILE factory on Punk Hazard.
The episode begins with Big Mom reaching out to Kaido in order to tell him that she will be heading to Wano (which is Luffy's next destination as well), and she's still angry that Luffy has seemingly gotten a major win off of her. Though Luffy did not battle Big Mom directly, the ruckus he caused during the Whole Cake Island arc has certainly damaged her pride. She's got to save face by killing Luffy.
But Kaido is in the same boat as Luffy has taken him down a peg in very much the same way. The interesting thing here, however, is that Kaido and Big Mom seemingly have a past. This must be tied into their roles as Emperors of the Sea, but much of this is still being kept a mystery for now. All fans get to see for now is that Big Mom is also planning to head to Wano, and she and Kaido will definitely clash when they see one another.
Without giving too much away, Kaido is Luffy's next big opponent in the Wano Kuni arc. This arc of the series seemingly will give the anime a major overhaul, and along with the new setting and art style, the other Straw Hats will be making a return as well.
Eiichiro Oda's One Piece first began serialization in Shueisha's Weekly Shonen Jump in 1997. It has since been collected into over 80 volumes, and has been a critical and commercial success worldwide with many of the volumes breaking printing records in Japan. The manga has even set a Guinness World Record for the most copies published for the same comic book by a single author, and is the best-selling manga series worldwide with over 430 million copies sold. The series still ranked number one in manga sales in 2018, which surprised fans of major new entries.