Yuna Yuki is an ordinary middle school student. She has fun with her friends , gets ready for school, would go to classes, participates in club activities, and gets up each day. However there is one extraordinary thing about Yuki -- she is one of the"Brave Hero Club." What does the Brave Hero Club do? Who's the mysterious being called"Vertex?" Yuki Yuna and her friends' story occurs in Year 300, Era.