In both the manga and its anime adaption, the story of Yu-Gi-Oh! has always been about the relationships that its characters have with one another. Whether it be rivalries between Yugi and Joey, friendships between Yugi and his friends, or romantic relationships between Rex Raptor and Weevil Underwood, seeing how these characters interact is a highlight of the show. Even if those interactions are usually over a children's card game. Gotta keep things flashy, ya know?
10 Yugi And Joey
Of course, Yugi and Joey's relationship is central to the show and manga. Yugi's wish when he first completed the Millenium Puzzle was to gain friends. After he made that wish, Joey, Tristan and Tea came along. While he does have a great relationship with Tea and no one cares about Tristan, his strongest relationship is with Joey. The man has dived into the ocean to save some paper trading cards for Yugi (actually sleeving them might have helped a bit), so it's clear that the two care deeply for one another.
9 Joey And Mai
Probably the only real hint of romance that we ever got on the show, Joey and Mai had a very close relationship. In Duelist Kingdom, Mai was shown by Joey and his friends that having friendships doesn't make you a weak person. Instead, they make you stronger.
While Mai initially resisted them, she then came to the aid of Joey by giving him her entry card for the tournament so he could fight Bandit Keith. She was then saved in Battle City by her friends, as well. This sadly was the last time we ever saw of Mai because Waking the Dragons is not canon and we refuse to acknowledge how dirty that arc did her. Nevertheless, the relationships that Mai formed during Duelist Kingdom changed her life forever.
8 Joey And Serenity
Ignoring the fact that Serenity's contribution to the anime was mostly just her screaming and/or crying (except that one time she did actually save Joey's life that was cool), her relationship with her brother was key to Joey's fight to the top in Duelist Kingdom. He stopped at nothing to help his sister and continued to do so throughout Battle City and the Virtual World arc. The two care for each other deeply, and would quickly sacrifice their own lives if it meant helping the other.
7 Marik And Ishizu
Marik and Ishizu were new additions to the franchise in Battle City, but they are the reason that the events of that arc played out. Marik was planning to take over the world, and Ishizu orchestrated the creation of Battle City in order to stop that plan coming to fruition. If Ishizu didn't care so deeply about her brother, she might not have been moved to such actions in order to help save him from the darkness inside him, making their relationship an important one to the show.
6 Yugi And Kaiba
Yugi and Kaiba's rivalry is one that prevails throughout the entire length of the show. As they are the top two duelists in the world, Kaiba will stop at nothing to take Yugi's place at the top, and Yugi isn't going to let him do that without a fight.
While they might be rivals, there were also numerous times that the two worked together for the greater good, as the respect that they had for each other was enormous.
5 Yugi, Joey, Tristan And Tea
The most iconic foursome in television history, that is not an opinion, but a fact. These four have been through thick and Dartz with each other and never gave in, no matter how plot-armory things got. No matter what they were faced with, their belief in each other never once lapsed. In the era of fake friends, we all need a Joey. Who could go without a Tea? And we'll take a Tristan, too.
4 Gozaburo And Kaiba
Gozaburo made Seto Kaiba into what he is today. A billionaire who spends most of his time playing children's card games and saying that he doesn't believe in this mumbo-jumbo. Iconic. While Gozaburo's actual presence in the show is limited mainly to filler arcs, his influence on both Seto and Mokuba is an important part of their character, and he is a figure that they'll never forget.
3 Bakura And Yugi
While Yugi faces countless enemies throughout the course of the show, in the end, it is Yami Bakura who is the final roadblock to Atem's goal. The two duke it out in the final fight... which was a tabletop game of ancient Egypt? Excuse us?
Either way, Bakura is a constant force in the anime that does not go unnoticed, always lurking in the shadows. He and Atem go a long way back (literally to ancient Egypt), and that history is a huge part of the show.
2 Mokuba And Kaiba
If there's one person that Kaiba isn't a human garbage can toward, it is his brother Mokuba. The two have been together their whole lives, and Kaiba would risk anything to make sure Mokuba was safe, even through his 38 kidnappings throughout the show. Come on, he even based a female character (lmao) in his video game off of Mokuba. If that's not love then what is?
1 Yugi and Atem
Of course, the most important relationship in the entire anime is the one between Yugi and the pharaoh. In the beginning, it started out as Yugi trying to comprehend that there was a second being living inside of him. But then, things slowly started to change. The two slowly started to understand each other and began working together.
Yugi and Atem were beside each other for every challenge they faced—not by choice they; literally share a body. They saw each other at their best, and also at their worst. Their bond is something that is unique to them, as no one can understand the relationship that the two shared.