The story takes place in Alberia, the kingdom where dragons live. All royal members in Alberia have the Dragon Transformation (shapeshifting in English) ability, where they can wield a dragon's power by forming a pact with a dragon to borrow their form in battle. One day, a strange occurrence begins to happen in this kingdom. The Holy Shard (Sacred Shard in English) protected by the capital starts to lose its power. In order to save his people, Euden, the Seventh Prince (Seventh Scion in English), who has not made a pact with a dragon, sets off on his Dragon Selection Trial.
The Seventh Scion Euden, the youngest prince of the kingdom of Alberia, is told by his father, the king Aurelius, to seek out Midgardsomar, the Windwyrm, to forge a pact after the Sacred Shard of the kingdom darkens. Such a holy object can only be moved by a pactbearer, and to replace the kingdom's Shard, he must forge the pact. He goes to Midgardsomar's home, the Mistholt with his sister Zethia and their friend, the faerie Notte. He forges the pact, meeting the Paladyn Elisanne and the mercenary Ranzal. When he goes to retrieve the Shard, he finds a woman named Cleo left to guard the Halidom, the former base of Alberius, and the castle's Shard. His father appears and tries to seize it, but Euden inadvertently shapeshifts until the Holywyrm Elysium. Regardless, Zethia is kidnapped by Aurelius.
Some time later, Euden, now leading the Halidom, receives word that Alberia was renamed to Dyrenell, and that it has declared Euden the 'traitorous prince'. He moves to defend a village from the attack of Dyrenell (meeting Luca and his sister Sarisse), and fights a Greatwyrm, Mercury. Mercury formed a pact with the haughty and narcissistic Prince Emile, which she breaks and instead forms a pact with Euden.
Next, they hear that Aurelius is attacking the Greatwyrm Brunhilda, the Flamewyrm. He saves the dragon, and forms a pact at her volcanic home, her joining him as 'Mym'. After that, he decides to form a pact with the Lightwyrm (and Greatwyrm) Jupiter. Emile reappears and tries to as well, but Jupiter chooses Euden over him. A mysterious woman then teleports the party to the Binding Ruins.
At the Binding Ruins, they once again encounter Aurelius and Zethia. Aurelius is revealed to be possessed by an evil entity, the Other. His possessor transfers himself to Zethia, and Aurelius dies. Zodiark, the last surviving Greatwyrm that is not pactbound to Euden, is revealed to be Aurelius's pactwyrm. Zodiark forges a pact with Euden. Euden's older brother Valyx arrives at the Halidom with an army. Euden declares the Halidom New Alberia, and resolves to fight Dyrenell.