In a realm known as the capital of the undead, Necrozoa, the episode begins with a flashback showing the victorious return of Leonis, now known as the King of the Undead, greeted by Roselia. They exchange gifts, with Leonis receiving a demonic sword that can only be drawn under a specific condition, which he already knows.

Back in the present, the city is threatened by a "Stampede" triggered by Arakael, a resurrected enemy from a past millennium. Leo, determined to rescue his servant Selia from Arakael's clutches, prepares to fight against him. Although Arakael is vastly different from his former self, having become a leader of the Void, his resurrection suggests that Roselia may still be alive as well.

As the city braces for the onslaught, Leo casts an 8th-level containment spell to protect the children at the Sunny Spot House, with whom Selia shares an emotional bond. He then sets out to rescue Selia, enlisting the help of Elfiné Phillet, a holy swordswoman, to locate her using the powers of her sacred sword.

Selia, abducted by the Voids, is held at the headquarters of the Assault Garden. Leo heads to the power plant with his demonic servants, Blackus and Shary. Shary, originally an assassin, is tasked with aiding the humans in their fight against the Voids.

The confrontation with Arakael escalates as he drains energy from the city's Mana Crystal, enabling him to cast multiple powerful spells simultaneously. Leo and his allies battle against Arakael's domain, which saps their mana. However, Selia, strengthened by Leo's mana-infused blood, joins the fight, determined to protect Leo and the city.

In a decisive moment, Leo claims the seventh Assault Garden as his own, declaring all its inhabitants his subjects whom he must protect. This act fulfills the condition to draw the demonic sword Dáinsleif. Wielding the demonic sword, Leo defeats Arakael, ends the Stampede, and saves the city.

The city recovers, and Leo and Selia reflect on the battle. Leo, now devoid of mana and physically exhausted, receives a handmade medal from the children he protected. Selia, in need of blood for her Sacred Sword, turns to Leo, leading to a humorous misunderstanding with her comrades.

The episode ends with a royal figure acknowledging the efforts of the Holy Swordsmen and deciding to thank them for defending the Assault Garden, hinting at future developments and the secret feelings of the princess.