A mysterious mental virus begins to grow and spread inside human bodies, yet people remain completely unaware—until the virus devours their flesh entirely and turns them into “Shou.” As the era of coexistence between humans and Shou unfolds, humanity gradually becomes accustomed to this strange new reality. But then, all at once, those rare humans who are immune to the virus suddenly vanish, leaving behind only scattered clues. In the present day, humans follow these faint traces, trying to uncover what really happened—and what the existence of the Shou and the missing immune ones truly means for their world.