Anyone who has, even superficial, knowledge Yu-Gi-Oh! would know that the main character is, of course, Yugi Muto. The series is primarily about his journey to becoming a duelist and a more confident person, in general, as he helps his other self discover the secrets of his past, and it's rare for a story not to have him as a driving force in one way. or other.
There's no arguing that Yugi is the protagonist of the original Yu-Gi-Oh! series, but that doesn't mean he's the most important character. It is common for stories inside and outside of anime to have characters other than the protagonist being those around whom the lore mainly centers, and certainly, there is a specific character in Yu-Gi-Oh! who was always a much bigger driving force of the plot than Yugi. This is true in both the anime and manga continuity, and it completely changes how one should view the Yu-Gi-Oh! franchise.
Why Seto Kaiba has always been the most important character in Yu-Gi-Oh!
If there is someone who could be considered more important to Yu-Gi-Oh!story, then it would have to be Yugi's rival, Seto Kaiba. Not only was he the first recurring antagonist in the manga, but Duelist Kingdom and Battle City are largely framed around events related to Kaiba and his family, and he ends up with as much development as Yugi and Joey, if not more. THE Yu-Gi-Oh! the manga wasted little time in making Kaiba the most important character in its loreand that's especially impressive when he was originally just another episodic villain for Yugi to deal with.
The story that best exemplifies Kaiba's importance, of course, is that of 2016 Yu-Gi-Oh! The dark side of dimensions. The film was supposed to be an epilogue to the original manga and a celebration of Yu-Gi-Oh!Kaiba's 20th anniversary, and while there's plenty of focus on Yugi's character, most of the story is driven by Kaiba's actions and his closing arc with Atem. Yu-Gi-Oh! using a big birthday special like The dark side of dimensions to further develop Kaiba's character emphasizes how important he isand the fact that Kazuki Takahashi personally wrote the film takes this even further.
Like the Yu-Gi-Oh! Makes Kaiba even more important than he was in the manga
Kaiba has an incredible presence in Yu-Gi-Oh! Anime
Kaiba is without a doubt the most important character in the Yu-Gi-Oh! manga, and the anime took this even further. To begin with, Yu-Gi-Oh!The Virtual World filler arc, which took up half of Season 3, was focused entirely on Kaiba's backstory, and this not only gave Kaiba a lot of character development, but also led to it being the only arc in which Kaiba defeated the main one. villain and not Yugi. THE Yu-Gi-Oh! anime making Kaiba the star of an original story for half a year shows how important his character has becomeand it only got bigger from there.
Although the manga ended Kaiba's story with Battle City, the same cannot be said for the anime's continuity. Kaiba not only created Duel Academy, the main setting of Yu-Gi-Oh! GX to Jaden and his friends, but Kaiba sent Jaden and Yubel's drawings into space, leading to the creation of the Neo-Spacers and Yubel's corruption by the Light of Destruction. All this means that Kaiba is most responsible for the events of Yu-Gi-Oh! GXand there was no character better suited for the role.
Yu-Gi-Oh! 5D it would also show how influential Kaiba's character has become in the anime. Although Kaiba does not physically appear in 5DKaibaCorp has become a tyrannical megacorporation responsible for transforming Domino City into the dystopian New Domino City, which means that Kaiba is the only character in the original Yu-Gi-Oh! have a presence in Yu-Gi-Oh! 5D thanks to the continued existence of KaibaCorp. It is true that KaibaCorp's presence is negative for half of 5Dbut the fact that Kaiba is the only character present in 5Deven if indirectly, it says a lot about how great he has become.
Kaiba being so important in Yu-Gi-Oh! Completely changes your story
It's hard to argue against the idea that Kaiba is Yu-Gi-Oh!is the most important character, and this completely changes the way you look at the series. Naturally, the original story is still primarily about Yugi and Atem's journey through life, but with the focus that Kaiba receives in the story, Yu-Gi-Oh! is a story about Kaiba's struggles and eventual legacy as much as Yugi's, if not more.
How one feels about this is another question, as it can be argued that much of the story is focused on Kaiba to the detriment of other characters, with even Yugi sometimes falling behind in terms of development. Without considering, Yu-Gi-Oh!The story would be completely unrecognizable without Kaibaand with how big and iconic Yu-Gi-Oh! has become over the last 20 years, it's hard to see this decision as anything other than the right one.