Duke of Hell as a Teacher

The Duke of Hell, Rama Allen, a powerful devil amongst the 7 Dukes. Has been betrayed by the Devil King due to the potential of rebelling against him. The 6 other Dukes defeated him and sealed him to nothingness, but now has come back 500 years later. With all of his powerful and impactful existence erased, he swears to gain more power kill the Devil King. But there was one problem, a girl who canceled his seal has now become his master, asks for help in her studies. Will he be able to get back at the Devil King while becoming a tutor for the girl?