One Piece's latest episode helped the anime steadily build to the climax of Luffy and Katakuri's fight in the Whole Cake Island arc as Luffy tries his hardest to master the Observation Haki.
The latest episode helps to bring Luffy one step closer as another important flashback to his training with Rayleigh gives him another key piece of information: relying on instinct.
In Episode 867, Luffy is steadily improving his use of the Observation Haki against Katakuri, but he's still struggling to keep up. Not only is Katakuri increasing the pressure on him with fiercer attacks, but he's being attacked from the sidelines by Charlotte Flampe's silent needles.
This onslaught has built to such a point, that Luffy is feeling more defeated than ever as it's becoming increasingly hard to concentrate. Concentration's one crucial aspect of mastering Observation Haki, as Luffy remembered from his previous Rayleigh flashback, but when he's completely at a loss, he remembers his training once more.
In the flashback, Luffy's blindfolded and manages to dodge one of Rayleigh's strikes when he imagines a small flicker of light. It's much in the same way it's been shown in the battle with Katakuri, and Rayleigh confirms that Luffy is on the right track. He says that imagination is one of the keys to mastering the Observation Haki, but what's more important is that he has to rely on his instincts.
Now that Luffy remembers that he's got to stop thinking about dodging attacks, and rather sense them all instinctively, it's already made major headway in the battle. Although he's still unable to fight back against Katakuri after this flashback, he importantly manages to dodge one of Flampe's needle attacks. Though it seems more like he just passed out coincidentally, it also seems like Luffy instinctively dodged an attack that he couldn't see before.
This is one more crucial step to putting Luffy on an equal playing ground against Katakuri, so the fight is surely only heating up from here. 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.