Yuna Yuki is an ordinary second-year middle school student. She gets up in the morning, gets ready for school, goes to classes, participates in club activities, and has fun with her friends. But there is one extraordinary thing about Yuki — she belongs to the “Brave Hero Club.” What does the Brave Hero Club do? Who is the mysterious being called “Vertex?” Yuki Yuna and her friends’ story takes place in Year 300, Era of the Gods.In the year 298 from the era of the gods, elementary school girls Sumi Washio, Sonoko Nogi, and Gin Minowa are tasked with an important mission. They are to become heroes and fight Vertex, a mysterious enemy that is attacking Shinju-sama, the god tree that protects Shikoku, the only area in the world that is still habitable. What they don’t know, is that this fight will cost them more than they could have ever imagined.