Yowai 5000-nen no Soushoku Dragon, Iwarenaki Jaryuu Nintei: Season 2

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?