I Was Tasked With Defeating The Demon Lord, But For Some Reason, She Is Now My Girlfriend!?

Synopsis

Newly hired Magic Professor, Lawrence Larkdale, is ready to start his quiet life as a simple teacher at the capital's most prestigious magic academy. But that dream is short lived as a mystic prophecy declares him the sole person who can bring peace to the warring human and Demon races by slaying the Demon Lord. Soon after, Lawrence finds himself deep inside the nearest Demon castle and face to face with the ruler of said castle, Lillim Zeroth Von Millionflame. Way out of his league to fight the powerful Demon Lord head on, Lawrence has to use his wits to get him out of it alive, but one misspeak and suddenly, he and the Demon Lord... are going steady???