The 18-Year-Old Demon King

Rabis Vindica, the son of the Great Demon King who rules the Demon Realm.
After acting on his own and wiping out a rebellious demon noble family, he is punished with banishment to the Human World.
Living in the body of an ordinary student, Rabis soon discovers that the demonic power he should no longer be able to use still reacts to evil.
As he gradually relearns how to wield his power, he begins searching for a way to return to the Demon Realm.