The time is the near future. Cockroaches and other household pests have become immune to all forms of insecticides. In response to this crisis, a Japanese company has created small, doll-like, insect exterminating robots called Hoi Hoi-san. A competing company has also released their own version, Combat-san. Because of their adorable appearance, these little robots have become somewhat of a phenomenon and have gained many fans. Late at night, in the home of one such fan, Hoi Hoi-san and Combat-san search for insects to exterminate... but Combat-san is not above trying to exterminate Hoi Hoi-san while she's at it.

Bullies often target someone frail and weak—someone exactly like Yuugi Mutou. His beautiful childhood friend, Anzu Mazaki, is always there to stand up for him, but he can't depend on her forever. Katsuya Jonouchi, who is almost always accompanied by his verbal sparring partner Hiroto Honda, doesn't seem like a bad person either, despite always bringing Yuugi trouble. But most of all, Yuugi wishes for a true friend who understands him and would never betray him. Yuugi treasures his Millennium Puzzle, an ancient Egyptian artifact that was brought into his grandfather's game shop. Believing that solving the puzzle will grant him his wish, he completes the puzzle, unleashing a new personality within him—the soul of the "King of Games." Dark, twisted, strong, and reliable, the new personality named Yami Yuugi is the exact opposite of Yuugi. Upon any injustice toward him, Yami Yuugi takes over Yuugi's body and forces the opponent into a "Shadow Game." The stakes are high as whoever loses shall have a taste of the darkness that resides within their own heart. [Written by MAL Rewrite]

Although Talpa has been defeated, the Warriors don't get much of a break. As they celebrate Ryo's birthday party, the news tells them of a strange killer in samurai armor wreaking havoc in New York. And the armor looks very familiar. Now, they will have to battle the ancient sorcerer Shikaisen for Sage's life!

In the great Garubado Empire, a lethal weapon is in the process of being manufactured, but is stolen and subsequently lost in battle. Now the Empire is looking for this weapon: a girl that can call forth the "Dragoon" power. She has amnesia and is found by a wandering swordsman in training by who vows to help her find out who she is and why she has such a strange power.