In the bustling and futuristic city of Heartland, a young boy named Yuuma Tsukumo has a dream that everyone his age wants to achieve—earning the title of the greatest duelist! Sadly, due to his lackluster dueling skills, this dream is far from achievable. But when the school bully, Ryouga "Shark" Kamishiro, splits the key given to him by his father into two pieces, he inadvertently sets Yuuma on a collision course with his dream. Retaining one half of the key, Yuuma begins a duel with Shark, but soon realizes that his inexperienced skills are no match for him. In a sudden turn of events, Yuuma's key repairs itself, and the "Door of Destiny'' appears before him. Using the key to open it, Yuuma is greeted by an alien by the name of Astral—a being only he can see. The bewildered Yuuma soon learns that his memories have been divided into 100 "Number Cards," all of which he must retrieve. However, he is also not the only one looking for them. Bombarded by these revelations, Yuuma, alongside Astral, must defend the world from the upcoming threats that loom over Heartland City—regardless of any divine intervention that may occur.

After discovering that his orphanage was on the brink of closing due to financial stress, Finn, who was living freely on the streets, set out for a casino with the aim of making a fortune. However, nothing could have prepared Finn for the nightmare that was awaiting him. Once there, Finn encountered a car chase and bloody shootout caused by a man's “lucky” card. Finn will eventually learn what the shootout was about. The world order can be controlled by a set of 52 X-Playing cards with the power to bestow different superhuman powers and abilities to the ones that possess them. With these cards, people can access the hidden power of the “buddy” that can be found within themselves. There is a secret group of players called High Card, who have been directly ordered by the king of Fourland to collect the cards that have been scattered throughout the kingdom, while moonlighting as employees of the luxury car maker Pinochle. Scouted to become the group's fifth member, Finn soon joins the players on a dangerous mission to find these cards. However, Who's Who, the rival car maker obsessed with defeating Pinochle, and the Klondikes, the infamous Mafia family, stand in the way of the gang. A frenzied battle amongst these card obsessed players, fueled by justice, desire, and revenge, is about to begin!

Kei Kunieda is a newscaster who strictly maintains an amiable and kind persona while at work. Although he smiles on the outside, he covertly curses at others to his heart's content. His everyday life is smooth, even if he keeps half of himself hidden at all times, but that changes when he meets Ushio Tsuzuki, an independent stop-motion animator. Soon, Kei finds himself caught in a lie borne from his two personas meeting Ushio under different conditions, with the other man unaware they are the very same person. As feelings begin to blossom between them, Kei cannot be sure if Ushio will love both sides of him—or only just half. [Written by MAL Rewrite]

With its gorgeous landscape and prosperous people, Great Japan is the envy of all other nations. But a serious threat hovers over the country. Mysterious guardians known as Master Samurai are Great Japan's only defense. At the behest of the student council, young samurai Muneakira Yagyuu arrives at Buou Academic School. Run by the Tokugawa Shogunate, here children of warriors are given aristocratic education required to run the country. The school is led by the student council president Yoshihiko Tokugawa and his sister Sen, who also happens to be Muneakira's childhood friend. Upon arriving at the academy, Muneakira finds himself in the midst of a terrible fight. During the chaos, the sky fills with a peculiar white light and a mysterious girl named Juubei Yagyuu appears and suddenly kisses Muneakira. With his kiss, she awakens an unknown power that protects them. Just who is this girl, and where did she come from? Muneakira finds himself entangled in the fate of the country and a threat that will shake Great Japan to its core. He must learn the secret behind the Master Samurai and the kiss that awakened Juubei's power in order to protect his country. [Written by MAL Rewrite]