"Magi: Sinbad no Bōken" is a prequel to the main "Magi" series, focusing on the early life and adventures of Sinbad, a legendary figure destined to become a king and a central character in the broader "Magi" universe. The story begins in the war-torn country of Parthevia, where a young Sinbad lives with his mother, Esra, after the death of his father, Badr. Struggling with poverty and the oppressive rule of Parthevia's corrupt leaders, Sinbad dreams of exploring the world and freeing his homeland from tyranny.

Sinbad's journey begins when he encounters Yunan, a mysterious Magi who guides him to a dungeon, a mystical labyrinth filled with treasures and dangers. By conquering the dungeon, Sinbad gains the power of a Djinn, a supernatural being that grants him immense strength and the ability to wield magic. This marks the start of his rise to prominence. Along the way, Sinbad forms alliances with key characters, including Drakon, a warrior from the Tison Tribe, and Hinahoho, a skilled sailor. Together, they establish the beginnings of what will become the prosperous kingdom of Sindria.

As Sinbad travels across the world, he encounters various nations, cultures, and political factions, each with their own struggles and ambitions. His charisma, strategic mind, and growing power attract both allies and enemies. The series delves into Sinbad's moral complexities, as he balances his desire to create a better world with the compromises and sacrifices required to achieve his goals. His interactions with figures like Serendine, a princess of Parthevia, and Barbarossa, a ruthless conqueror, highlight the challenges of leadership and the consequences of ambition.

The narrative explores themes of destiny, freedom, and the cost of power, as Sinbad's actions shape the future of the world. His journey is marked by personal growth, as he evolves from a determined but naive boy into a visionary leader. The series also provides insight into the origins of the Seven Seas Alliance, a coalition of nations that plays a pivotal role in the broader "Magi" storyline. Through Sinbad's adventures, the series expands the lore of the "Magi" universe, offering a deeper understanding of its history and the forces that drive its characters.