Yu-Gi-Oh! tells the tale of Yugi Mutou, a shorter-than-average high school student who was given the fragmented pieces of an ancient Egyptian artifact, the Millennium Puzzle, by his grandfather. Upon reassembling the Puzzle, he is possessed by another personality who is later revealed to be the spirit of a 3,000-year-old Pharaoh (5,000-years-old in the English anime) called Atem, with no memory of his own time. As the story goes on, the two of them (together with Yugi's friends), try to find the secret of the Pharaoh's lost memories and his name, with the Duel Monsters card game being an ever prevalent backdrop or plot device.
Yu-Gi-Oh! GX is set 10 years after the first series. It follows the story of Jaden Yuki (Judai Yuki in the Japanese version), a young talented duelist who is given the card "Winged Kuriboh" by Yugi before Jaden's admission to Duel Academy (Duel Academia in the Japanese version), an elitist boarding school established by Seto Kaiba. Jaden (who receives low marks in his admission tests), is placed in the Slifer Red dormitory (Osiris Red), which is reserved for students with the lowest grades. The story goes on as Jaden faces challenges from different students in Duel Academy. He later finds himself entangled in a conflict related to the hidden secrets of the academy.
Yu-Gi-Oh! 5Ds is set in a distant future where the residents of the poverty-stricken town called Satellite provide the manpower to sustain a utopia called New Domino City (Neo Domino City in the Japanese version), a futuristic version of the city of Domino where some of the events of the original Yu-Gi-Oh! took place. The story centers around five characters known as Signers, who have birthmarks bearing one part of a monster called the Crimson Dragon (which saved the world in the past,from the Earthbound Immortals). The main character, named Yusei Fudo, is a Signer. Each Signer has a dragon monster. In later episodes, they fight Dark Signers—duelists who try to revive the Earthbound cards.
The early chapters of Yu-Gi-Oh! feature a variety of different games; but from the Duelist Kingdom arc onwards, the focus is shifted to a card game called Duel Monsters. Duel Monsters is played using a holographic image system created by Seto Kaiba (following his first Shadow Game with Yugi). In the manga and first series anime, these were initially performed on tables, using holographic tubes, while the second series anime uses huge holographic fields. Starting with the Battle City arc, (as well as the series that followed), duels are performed using portable Duel Disks, invented by Seto Kaiba, which allows duels to happen anywhere.
Ryo Bakura (獏良 了, Bakura Ryō?) is a fictional character and the main Antagonist in the manga and anime series Yu-Gi-Oh!. In the English Duel Monsters anime, he is known as simply Bakura, and in the English Yu-Gi-Oh! The Eternal Duelist Soul video game, Bakura's name is given in the traditional Japanese order and is rendered Bakura Ryo.
Introduced as a new exchange student early on in the series, Bakura quickly befriends Yugi Muto and his friends and remains their friend for much of the series. However, Bakura possesses the Millennium Ring, an ancient Egyptian artifact that, unknown to Bakura, houses an evil spirit that plots to steal Yugi's Millennium Puzzle and becomes a major antagonist during the Memory World arc. Eventually, Bakura's good side is almost entirely suppressed and he is continuously controlled by the spirit, except in rare moments where he is separated from the Ring or able to overpower the spirit.
While on a trip in Egypt, Bakura's father, the curator of the Domino City Museum, purchased an ornamental ring from a street peddler, which he gave to his son because - according to the animated series - it was connected with the Duel Monsters card game, which Bakura was fond of. In truth, this unassuming object was the Millennium Ring, one of the seven mystically-empowered Millennium Items. Contained within the Millennium Ring was an evil spirit, which took possession of Bakura, and came to be known as Yami Bakura ("Dark Bakura," in English). Unlike the similar relationship between Yugi Mutou and the spirit of his Millennium Puzzle, the spirit of the ring is a malignant entity, and completely suppresses Bakura's soul when it takes over his body.
Beyond these facts, however, the actual identity of the Spirit of the Ring is fraught with complication. Writings about the series would often state that the spirit within the ring was that of a tomb robber from ancient Egypt (who would later be named "Thief King Bakura", detailed below) and Yami Bakura delivered several remarks that corroborated the claim, without explicitly identifying himself. Conversely, however, during the manga version of the final story arc of the series, Dark Bakura explicitly identifies himself as a fragment of the soul of the Dark God, Zorc Necrophades... and yet, within the same story, also refers to the thief's soul existing within the Millennium Ring. Although not discussed in detail in the anime (where the reference to the thief's soul is not made, and Yami Bakura is identified only as Zorc), the manga establishes that Zorc is capable of possessing other beings, and that eventually, his soul becomes "as one" with those of these victims (specifically, this was described as happening to the High Priest Ahkenaden), so from this, it may be presumed that the Spirit of the Ring is the soul of Thief King Bakura, subsumed by that of Zorc Necrophades.