The last few episodes have set the table for the final stretch of Luffy and Katakuri's battle on One Piece, and the Whole Cake Island is about to come to a grand close with the debut of a brand new Gear Fourth form.
Though Luffy's newest Gear Fourth version won't be fully revealed until the next episode, the latest episode ends by making an appropriately huge introduction for Gear Fourth Snakeman.
Ever since Luffy made his way back to the Mirro-World for the second phase of the fight with Katakuri, he has been struggling to land any decisive blows. This changed in the latest episode, however, as the two of them are beginning to wear themselves down thanks to the drawn out nature of this brawl. Luffy seemed to get the closest he ever has to mastering the Observation Haki, and he's beginning to find gaps in Katakuri's defense.
But their final stand against one another cemented that this truly is the final stand in the fight overall. Luffy decides to unleash one more Gear Fourth form, something fans have never seen. This transformation reveals a more slender version of Gear Fourth, with much wilder hair. It's also accompanied by a pillar of smoke that curl and twist to look like snakes.
As for what makes the Snakeman form more viable in the fight against Katakuri than previous forms, the preview for the Episode 870 already seems to hint at how much of an improvement Snakeman has for Luffy. Incorporating his knowledge of the Observation Haki along with what he's learned about Katakuri over the course of the fight, this form is Luffy's last ditch effort. While fans of the manga know where this is heading (and have been especially excited for this form to debut in the anime), there's no telling what kind of level the anime will bring Snakeman to.
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.