Five years ago, all but one of the inhabitants of Ootsuka village perished due to the plague… but the lone survivor wished only to follow her two dear friends to the grave.

To prevent the death 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 have since sought refuge in a church near the adjoining village.

Eventually, the Imperial Church begins to express its interest in possessing "Murasame", the demon blade rumored to contain life… but what connection does this legendary sword have with the three survivors of that devastating epidemic?