Yukari Tamura

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 believes in. One day, in the ruins of an Elf city, he meets Schwi, a female exiled "Ex Machina" android who asks him to teach her what it means to have a human heart.

Ciel learns of a "Aurora Society", that is rumored to be researching how to bring the dead back to life. Their next meeting is scheduled to be conducted on the ship Campania, voyaging across the Atlantic Ocean. Much to Ciel's dismay, Elizabeth "Lizzy" Midford, is taking the same ship, thus leaving him with no choice but to get aboard as well.

One year after the events of the anime, Rintarou begins to feel the repercussions of extensive time travel, and eventually completely fades from reality. Kurisu, being the only companion to remember him, now must find a way to bring him back.