From MangaHelpers:

As the current generation dragon warrior, Riu Feifon has been passed down the ability to call upon the dragons for their support in defeating evil. So when an evil dragon takes over a neighboring city, Feifon calls upon the dragon realm for their power. But what she gets is Sentokun, a red dragon that has been imprisoned and sealed off for rebelling against the emperor. Feifon has to somehow convince Sentokun to help if she has any chance of defeating the evil forces threatening the city. [vyc]