Six thousand years before Sora and Shiro were even a blink in the history of Disboard, war consumed the land, tearing apart the heavens, destroying stars, and even threatening to wipe out the human race. Amid the chaos and destruction, a young man named Riku leads humanity toward the tomorrow his heart believed in. One day, in the ruins of an Elf city, he meets Shuvi, a female exiled “Ex-machina” android who asks him to teach her what it means to have a human heart.
January 1999: Apprentice mage Azaka Kokutou, Mikiya’s younger sister, has been ordered by her mentor, Touko Aozaki, to investigate a certain incident in which fairies steal the memories of students at Azaka’s school, Reien Academy. Azaka launches an investigation with the help of Shiki.