Shuumatsu Nani Shitemasuka? Isogashii Desuka? Sukutte Moratte Ii Desuka?

500 years ago, humanity was massacred by mysterious and formidable beasts. Now, other races are threatened despite living on floating islands. Only a group of young women, the Leprechauns, manage to repel the enemy's assaults with the help of ancient weapons. Despite this, they know that each confrontation can mean death...

It is in this context that a young man appears after 500 years of sleep. He is the last human left in the world.