Nine hundred years have passed since the day that changed Mokou forever — long enough that she cannot even remember what that day was. Having wandered unknowingly into a fantasy land, she finally meets someone who does not avoid her: Keine, a half-youkai historian with the supernatural ability to perceive the past. Keine takes Mokou on a journey to rediscover what she has lost. And though Mokou can never truly die, her body still carries mortal fragility — consumed often by her own fiery power. She always regenerates. She can always try again.