Desperate to defend her village from the demon king, Reiko offers herself to a 5,000-year-old dragon for his help in exchange, but the flame-breathing beast is vegetarian and a total weakling. Together they embark on a journey to take down the demon king. With her dragon comrade, Reiko claims that she's his disciple, able to draw from his infinite powers, but is it really from him?

A 5000-year-old herbivorous dragon was living peacefully when one day a young girl showed up in his cave. She offered herself as a sacrifice in order to gain favor for her village. He played along as the great "Evil Dragon, the Demon Lord's Army Leader" in order to get rid of her. However, his little white lie awoke her hidden powers and his peaceful life suddenly ended.

The old herbivorous dragon, who gets mistaken for an evil dragon, and Reiko, a young girl with miraculous powers, arrive in a totally new country, Asgar, where the herbivorous dragon keeps taking the blame when he gets caught up in an elaborate conspiracy. Even though he just wants to live a peaceful life, the herbivorous dragon is continuously getting stuck in his role as the evil dragon and walks further and further down the road towards overthrowing the demon king.