Following the resolution of the deadly conflict with Link Joker, the world was once again at peace. However, Kai Toshiki is faced with an unexpected problem - Sendou Aichi, the world's hero who saved them all from Link Joker's invasion, has vanished without a trace. To make matters worse, everyone's memories of Aichi have vanished as well. With few leads to go on, Kai sets out on a quest to find Aichi, armed only with his "Blaster Blade" and the Royal Paladin deck that serve as a symbol of their bond. Kai soon encounters a group of elite warriors known as the "Quatre Knights" - Gaillard, Neve, Ratie, and Sarah. These fighters possess tremendous strength in vanguard battles and wield a mysterious power in their attempt to discourage Kai from searching for Aichi. But why are they trying to stop him, and how are they connected to Aichi? With his newfound "Legion" power, Kai fights to save Aichi. The battle for Aichi has begun!