Oda is the legendary author behind One Piece and, over the years, he has crafted this fantastic world that has lodged itself in the hearts of millions of fans. Oda's storytelling is the biggest strength of One Piece and, ever right from the first chapter of the series, it has been quite evident that his skills as a writer are incredible.
One Piece features some very complex plotlines and while some of them were crafted by Oda at the last second, there are others that were carefully planned for years before being incorporated into the arcs.
8 The SMILE Fruit Plot
The SMILE Fruits were incredibly important to the overarching plot of the Four Emperors Saga, especially the Wano arc, where the truth about them was finally revealed. These SMILE Fruits were artificially created Devin Fruits that granted powers to one in 10 fruit users, however, the other nine failures gained the Devil Fruit side effects, as well as lost their ability to express any emotion other than smiling and laughing.
The SMILE Fruit plotline was actually conceived long before the timeskip. They were mentioned for the very first time on Sabaody, when Doflamingo was speaking to Disco.
7 Sanji As A Prince
Sanji is the cook of the Straw Hat Pirates and one of the most important characters in the series. As a part of the East Blue 5, he is at the core of the Straw Hats, and, as a result, Oda tends to throw some more attention his way. Sanji was revealed in Whole Cake Island to be a Prince of the Germa Kingdom.
This came as a shock to the vast majority of the fans, however, Oda had planned this years in advance. In fact, hints about it were dropped as early as the Arabasta Arc and, at the same time, the Sky Island Saga also dropped subtle bits of information about Sanji actually being from the North Blue.
6 The Vinsmoke Siblings
Along with Sanji's royal bloodline, Oda also introduced the Vinsmoke Siblings during the Whole Cake Island arc. Once again, this is another major thing that he had planned long before it made it to the story.
Initially, Oda was not sure how many siblings he would give Sanji. However, thanks to Osomatsu-san being one of his daughter's favorites, Oda decided to incorporate the idea of quadruplets into Sanji's backstory, thus giving rise to the Vinsmoke siblings.
5 Time Travel
Time travel is another major thing that Oda planned years in advance in One Piece. This major revelation was made during the Wano arc of the story, where Kin'emon revealed that he, along with Momonosuke, Kanjuro, Kikunojo, and Raizo have come from the future.
While the fans were certainly shocked at finding this out, hints for it were provided to the fans years ago, during the Zou arc, where Momonosuke mentioned that he had met Roger, despite being just 8 years old. At the time, fans dismissed it as one of his lies, however, it proved to be significant later on.
4 The Concept Of Haki
The concept of Haki was properly explained to the fans shortly before the timeskip of One Piece. However, this concept was actually written into the story from the very beginning. When Luffy was saved by Shanks, the latter used Haki to scare away the Coastal King. Furthermore, as the story continued, different forms of Haki kept being shown.
In Jaya, Blackbeard openly mentioned the word Haki for the very first time when measuring Luffy's strength. On Skypiea, Mantra was introduced and, going down the line, different forms of Haki were incorporated into different arcs before the concept was finally explained to the fans after the Paramount War.
3 The Introduction Of Sabo
Sabo is a character that the fans were properly introduced to in the flashback of Luffy. He was presumed to have died in the flashback, however, in Dressrosa, Sabo was revealed to be alive.
Sabo is a character that a lot of fans assume to be a last-minute addition to the story. However, his character was planned years in advance. Ace's tribute to Sabo through his crossed-out tattoo had actually existed from his very introduction.
2 Kuma Breaking Up The Straw Hats
When Kuma first appeared in 2002, Oda had already drawn elaborate plans for his character. Oda revealed to his editor that Kuma would later be responsible for splitting apart the Straw Hat Pirates.
This ended up coming true in 2008, 6 years later, when the crew was separated on Sabaody Archipelago using the Devil Fruit ability of Bartholomew Kuma.
1 Nika
Nika, the Sun God, was introduced very recently in One Piece towards the climax of the Wano arc. However, the concept of Nika was actually planned by Oda long ago. In fact, the Sun God was actually mentioned for the very first time during the Skypiea arc. The winged races were revealed to have a connection to Nika.
At the same time, Fishmen who were discriminated against ended up creating the Sun Pirates under Fisher Tiger. Furthermore, the hoof of the Celestial Dragon was also covered up with the mark of the sun. If that wasn't enough, Otohime often compared life under the sun to freedom. Clearly, Oda had planned the Sun God Nika plotline years in advance and incorporated it into the story in Wano.