Five years ago, all but one of the inhabitants of Ootsuka village perished due to the plague... And the sole survivor wished only to follow her two dear friends to the grave. To prevent the deaths of the people who were like family to him, one of the dying boys used his last remaining breath to agree to a proposal put to him by a mysterious fair-haired man. Miraculously restored to health, the trio sought refuge in the adjoining village's church.

The story begins when the Imperial Church starts to express its interest in possessing Murasame, the demon blade rumoured to "contain life." But what connection does this legendary sword have with the three survivors of that devastating epidemic?