Twelve-year-old Win Kirifuda, a cheerful and somewhat eccentric boy living in the coastal town of Shirahama, lives and breathes the card game Duel Masters. His life takes a dramatic turn when he obtains a mysterious card from the Darkness Civilization, the Abyssbell=Jashin Emperor. This is no ordinary card; it is a vessel for a mischievous yet ancient dark god, whom Win affectionately nicknames Jashin-sama. Upon their first encounter during a local shop tournament, Win unwittingly awakens the dormant power of this "Evil God," setting the stage for an unprecedented upheaval in the Duel Masters world.

Unlike the previous protagonists of the long-running series who specialized in Fire or Light civilizations, Win is the first main character to wield Darkness as his primary civilization. His deck focuses on the new Abyss race, employing tricky, unconventional strategies powered by Jashin-sama's abilities. When Win duels using this dark deck, a special field called Jashin Field materializes, making the creatures appear real. A signature quirk of their partnership is that if Win wins a duel, the opponent must endure a penalty game known as "Jashin Time," though this is played more for comedic effect than genuine malice.

The initial storyline begins with Win entering a tournament where he meets his core group of friends. This includes the athletic and sensible heroine Karen, the cautious and bespectacled Ugata, and the eccentric Bowie Obochiyama. Together, they come into conflict with the D4, an elite group of four powerful duelists led by the arrogant Prince Kaiser. After Kaiser humiliates Win's father and burns his cherished deck, Win must learn to control his own inner darkness and master the power of the Abyss to challenge the D4 and prove that dueling is about passion and fun rather than cold, calculated victory.

Following his initial triumph over Prince Kaiser, the narrative continues into the "Duel Wars" arc. Win is invited to attend Maihama Academy, a prestigious school dedicated to the study of Duel Masters. Expecting a paradise of non-stop battling, Win is instead frustrated by the academy's strict, lecture-heavy curriculum. Determined to bring excitement back to the game, he establishes the "Duema Saikou Club" (The Ultimate Duel Masters Club) with his friends. However, the school holds dark secrets, as a mysterious entity manipulates events from the shadows, and Win must navigate new rivals and tournaments to protect his club and uncover the truth.

As the manga progresses into later volumes, the scale of the conflict expands beyond schoolyard rivalries. A malevolent faction known as the Moon Army, led by the vengeful Sabato, attacks Maihama Academy. Sabato, a former member of the D4 who despises Prince Kaiser, seeks to drain the fun out of Duel Masters entirely. This arc forces Win to confront a genuine existential threat, pushing his bond with Jashin-sama to its limits as they fight to defend their friends and the very soul of the game they love.