900 years have passed since that fated day that changed Mokou forever. It's been so long, she can't even remember anymore. Having crossed into a strange land of fantasy without realising it, she finally meets someone who doesn't try to avoid her - Keine, a half-youkai historian. With her ability to supernaturally learn the past, she takes Mokou on a journey to rediscover it. But although Mokou can never die, her body still has mortal fragility, and is often consumed by her own fiery power. Not to matter; able to regenerate from nothing, she can always keep trying until she gets it right.