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!

Tricked into assassinating his own prospective father-in-law, righteous samurai Raizou Kurima is overwhelmed with guilt. In order to reclaim his honor, Raizou swears vengeance on the lord who gave him those misleading orders. In his pursuit, he is aided by self-proclaimed merchant-of-all-trades Yuuen Usui, who is actually one of the Revengers—assassins who seek justice for the wronged and dispense bloody revenge on their behalf. Tragedy seems destined to follow Raizou as he becomes increasingly intertwined with members of the Revengers. As he begins working as a vigilante alongside them, the complicated web between the corrupt Japanese political elite, the unscrupulous Europeans, and the Revengers gradually reveals itself. The more entangled he becomes in these affairs, the more Raizou realizes that justice is as deceptive as the honor that he sought to redeem.