Action Duels, which allow duelists to soar and swing alongside their Duel Monsters, are taking the world by storm. Due to an evolutionary breakthrough, the Solid Vision system is now able to provide Duel Monsters with mass. Yuuya Sakaki is Yuusho Sakaki's son, the latter being the founder of You Show Duel School in Miami City. Yuusho insists that duels are not a tool of war, but rather are to bring smiles to people and thus introduced the concept of Entertainment Dueling. However, at the height of his fame, Yuusho disappears and fails to attend his duel with Strong Ishijima, the Action Duel champion. Although scarred by this sudden leave, Yuuya vows to become an Entertainment Duelist like his father. Several years later, in the midst of a battle with Strong Ishijima, Yuuya's desperation to win brings forth a miracle. His pendant begins glowing, turning his cards into Pendulum Cards, which enables him to perform a Pendulum Summon—a summoning method unknown to the world and himself—gaining him fame overnight. As a result, Reiji Akaba, CEO of Leo Corporation and founder of the elite Leo Duel School, starts producing new Pendulum Cards to incorporate Pendulum Summoning into the system. Thus, the mysteries that surround Pendulum Summoning and Yuuya's father start to unravel, and Yuuya learns bit by bit what it takes to become an Entertainment Duelist.

Yusuke Urameshi is not exactly what you'd call an angel. In fact, some might call him down right devilish. But when he dies in an accident trying to save a child, he finds himself in the Spirit World. Unfortunately for Yusuke, his name is not listed in the Book of Enma, which means it was one big mistake! So he should return from the Spirit World, but must pass a few tests first, and become a detective of the spiritual world. So now Yusuke works in the Spirit World as a half-dead, half-alive agent for Koenma, son of the ruler of the Spirit World. This position does have its disadvantages, especially when you're trying to enjoy your summer vacation and Koenma gets kidnapped! So now Yusuke must interrupt his summer fun to find Koenma and trade the Golden Seal of King Enma for his life. But if someone other then King Enma has the Golden Seal there will be chaos in the Spirit World! What's a half-dead spirit detective to do? With the aide of his closest allies, Yusuke sets off for Magma Valley, to save the life of the one who saved his, and find out who's at the bottom of this evil conspiracy. (Source: AnimeNfo)

While riding with Jack Atlas and Crow Hogan, Yuusei Fudou's Stardust Dragon is captured by Paradox, a mysterious Turbo Duelist from the future, during a Turbo Duel and turned into a Sin Monster. With the help of the Crimson Dragon, Yuusei chases after Paradox as he enters a time slip, ending up in the past. During this time, Paradox duels against Jaden Yuki, who is still able to use the powers of Yubel and The Supreme King. However, by this time Paradox had also captured Cyber End Dragon and Rainbow Dragon and overwhelms Jaden. He is saved thanks to Yuusei and the Crimson Dragon. Jaden informs Yuusei of Paradox's true intentions. By stealing various monsters from across time and turning them dark, he plans to kill Maximillion Pegasus, the creator of Duel Monsters, preventing the game from being created and causing the events of all three series to never happen. Yuusei and Jaden agree to pursue Paradox, which leads them to the past and causes a meeting with the King of Games, Yuugi Mutou. However, by the time Yuusei and Jaden arrive, Paradox had already attacked his time, supposedly killing both Pegasus and Yuugi's grandpa, and had also managed to steal Blue-Eyes White Dragon and Red-Eyes Black Dragon. After explaining everything to Yuugi, he agrees to fight with Yuusei and Jaden against Paradox in the ultimate three-on-one duel to free the trapped monsters and save both the world and time itself before it's too late. (Source: Wikipedia)

Millennia ago, a war was fought between the Netherworld and the Spirit World. Ultimately, the Netherworld was destroyed and Lord Yakumo, the King of the Netherworld, was banished to the depths of space. Now, five defenders from the Spirit World must team-up against Yakumo's Demon-Gods for possession of five, mystical sites. But Lord Yakumo is dangerously close to reclaiming the Power Sphere—the source of the Netherworld's energy—and once it is again in his possession, our world will become the new Netherworld. (Source: AniDB)