During their travels through the Unova region, Pokémon trainer Ash Ketchum, his faithful Pikachu, and his friends Iris and Cilan arrive in Eindoak Town. This settlement is built around a castle known as the Sword of the Vale, the site of an annual battle competition that Ash is eager to enter. During the tournament, Ash's Pokémon perform with surprising strength, winning battles they should have lost. The reason for this unexpected success is soon revealed to be Victini, a shy, mythical Pokémon with the power to lend its energy to others. Having witnessed Ash’s kindhearted attempt to rescue a wild Pokémon on a steep mountainside, Victini secretly took a liking to him and began boosting his team’s power from the shadows.

The town and its castle hold a deep and tragic history. Long ago, this place was the center of a prosperous kingdom known as the Vale, which thrived thanks to a flow of energy called the Dragon Force. The kingdom was protected by a king and his partner, Victini. However, conflict arose when the king's two sons went to war, each aided by a legendary dragon Pokémon: Reshiram, who seeks truth, and Zekrom, who stands for ideals. The war drained the dragons and disrupted the Dragon Force, threatening to destroy the land. To save his kingdom, the king used Victini's power to lift the castle into the air and move it to a new location, but this act unintentionally trapped Victini within a barrier called the Pillars of Protection, preventing it from ever leaving the area around the castle.

Now, a descendant of the original people of the Vale named Damon is determined to restore his ancestors' lost kingdom to its former glory. A well-intentioned but misguided extremist, Damon believes any sacrifice is worth the goal of reviving his people's home. He has already gained the allegiance of the legendary Pokémon Reshiram and plans to capture Victini to harness its limitless energy. He intends to use this power to move the castle—and Victini—back to its original location, an act that would not only trap the mythical Pokémon but also unleash the unstable Dragon Force, threatening to destroy Eindoak Town and the surrounding land.

To save his new friend Victini and stop Damon, Ash must seek the counterpart to Reshiram: the legendary Zekrom. The dragon of ideals only reveals itself to someone with a strong and pure heart. As Damon's plan unfolds and the Sword of the Vale begins to lift into the upper atmosphere, putting everyone in danger, Ash must convince Zekrom to join him. The film culminates in a desperate rescue, where Damon, realizing the catastrophic consequences of his actions, attempts to help Ash and Victini. Ultimately, Ash's belief in his ideals allows Zekrom to intervene, saving Victini and breaking the ancient barrier, finally granting the Victory Pokémon the freedom to explore the world beyond the castle walls.