What Do You Do at the End of the World? Are You Busy? Will You Save Us?

Humans have been driven to extinction by "Beasts". The duty of fighting the Beasts fall to "Fairies", who are destined to use their powers to wield "Holy Swords" called "Kariyon" and eventually meet their destiny of death. A sole human being named Willem wakes up after several hundred years, and continues his fight against the Beasts.