The Day the Devil was Born.Yugo confronts Yuri, while Aster moves on ahead to look for the Doctor. Leo reveals that the ARC system he was credited with creating actually originated from the United World, which is a realm possessing all four summoning methods. As Leo used this technology to enhance the game of Duel Monsters and bring life to the monsters, a duelist named Zarc began to use the solid mass of the monsters to duel violently against his opponents. As Leo tells the story, Yugo and Yuri's dragons start to once again cause an occurrence within Yuya and Yuto. It also affects Stargazer and Timegazer Magicians, which Riley is able to sense due to his experience as a war victim. After rising to the top of the duel world, Zarc suddenly used his dragons to wreak havoc across the world before combining with them to become the ultimate monster known as the Supreme King ZARC.