Yuuki Yuuna wa Yuusha de Aru: Washio Sumi no Shou S01

In the year 298, during the era of the gods, third-year students Washio Sumi and Sonoko Nogi and Gin Minowa were summoned for a crucial mission. They will become heroes and battle against Vertex, a mysterious enemy that attacks Shinjo-Sama, the god of the tree, who protects Shikoku, the only region in the world where people can still live. The only thing they know is that this battle will be much more than they can imagine.