The episode takes place in a world ruled by gods, spirits, and magic. Leonis Death Magnus, the last Demon Lord, is defeated by the Six Heroes and vows to return in a thousand years. Riselia Ray Crystalia, or Selia, belongs to the 18th Platoon of the Excalibur Academy of the Seventh Storm Garden. She is tasked with searching for Void Nests in underground ruins. Voids are mysterious creatures that appeared 64 years ago and are considered enemies of humanity.

During their investigation, Selia and her maid Regina discover a magical door. While attempting to decipher the inscriptions, Selia encounters Leonis, who has been reborn as a boy and is trapped inside a crystal. She frees him, and the two continue exploring the ruins. Leonis is confused by the new world and decides to keep his identity a secret to gather information.

Suddenly, they are attacked by an Ogre-class Void. Selia and Regina, who arrives just in time, fight against it. Selia is injured, and Leonis reveals his magical abilities to destroy the creature. He also heals Selia's wounds with his limited powers. The episode ends with Selia, Regina, and Leonis approaching the Seventh Garden of the Offensive, humanity's last stronghold against the Voids.