August and his companions had stepped up to challenge the demon lord who threatened to annihilate the entire world. In the end, their heroic spirit was for naught as they all perished at the demon lord's hands. Meanwhile, Yuu, a kindergartener in modern-day Japan, unexpectedly regains his memories of being a hero. To the bewilderment of his family, Yuu diligently devotes himself in preparation for the demon lord's definite return. With the goal of defeating the demon lord, Yuu, who is now a high schooler, sets up a "Hero's Club" in an effort to gather his former companions...?!