In the Laniakea Kingdom, humans live alongside powerful beings known as dragonfolk, who are distinguished by their tails and immense abilities. More than ten years have passed since the assassination of the supreme leader, the Dragon King. In a remote corner of this kingdom, a human girl named Jio dreams of escaping the quiet countryside where her father has forbidden her from leaving, yearning for the adventure that fills the stories of her hero, the legendary explorer Yuri Holst.

Her life changes forever when she encounters a mysterious amnesiac young man on the beach. Jio names him Nereid, and soon after, her village is attacked by Yerkes, a dragon knight of the kingdom. Yerkes reveals that Jio is the daughter of the accused assassin Yuri Holst, and that the entire world is hunting her because of her father's alleged crime. Just as she is about to be executed, Nereid manifests his own hidden dragonfolk powers, saving her life and revealing that his lost memories are somehow connected to Yuri Holst as well.

Forced to flee her home, Jio finally leaves her island behind, embarking on the adventure she always wanted under terrifying circumstances. Accompanied by the powerful but amnesiac Nereid, Jio sets off across uncharted waters and strange lands to find the truth. She seeks to clear her father's name and to understand why the world believes he killed the king, while Nereid hopes encountering the explorer will restore his missing past.

The world is filled with dragonfolk, and the strongest among them, the Zodiac Knights, are said to possess power matching entire military fleets. As Jio and Nereid journey through the kingdom, they face threats from the government agents who still pursue them, including powerful dragon knights. They also encounter various inhabitants of this world, such as allies like the living legend Yuri Holst, whom they seek, and formidable opponents including Susie the Kangaroo Dragon and a dragon knight named Chalk. The narrative revolves around the duo's quest for the missing explorer, the mystery of Nereid's identity, and the political turmoil following the Dragon King's death.