A city from an ancient civilization was discovered, from long before their people or the Grimm existed. And within? A robot of remarkable strength. The one known as X. Awoken in a time and place he does not know, and faced with a past he cannot remember. How will X make his way in this strange new world? And how will the world cope when the past comes back with a vengeance?

Mikasa wore the scarf wherever she went, ever since that night when she became the lone survivor in a cabin full of dead bodies. Armin was the only other person who understood that while Eren Yeager died protecting her, he didn't move on. Ghost!Eren.

In the process of solving his latest case, Phoenix becomes acquainted with a spirit called Sissel. But when another puzzling murder occurs, the two of them must join forces if they hope to prevent further tragedy. And who are these odd foreigners?