Ayanashi Series

Humanity ekes out an existence underground, hiding from monstrous creatures that dominate the surface world. Only the special warriors known as Ayanashi possess the power to defeat these impervious beings. The story ignites when a mysterious, wounded boy named Holo enters the lives of two siblings, only for a devastating monster attack to force his hand. He wields a flaming sword, igniting a desperate quest to reclaim the surface and bring light back to a world shrouded in darkness.