Private investigator Rin Asogi cannot die. Killed, she simply wakes up again, memories intact across six and a half decades of cases. Her newest client draws her toward Apos, an immortal being tied to the world tree Yggdrasil who is hunting Rin's memories for a ritual sacrifice. Working the case alongside her assistant Mimi, Rin is pulled into a string of murders in modern Tokyo that keeps circling back to what Apos actually wants from her.