Jason would've tried to live a normal life, after transmigrating into a strangely familiar alternate dimension, where Class and Levelling up was a thing, but soon he finds out he was a contractor of a Great Demon, who acclaims to make his life a miserable hell.

Jason, once an attorney at law, but now a Great Demon's advocate.

Through one magical event, his life changed. From living in a rundown apartment, he became heir to the fallen Great House of Locksmith.

He would need all his wits, intelligence, courage, and some magical power of his own if he wants to keep his life. However, all hope was not lost, and coupling with the knowledge he was imparted through the game, he strives to make the world a better place, putting all his wits and intelligence to use.

Follow Ian as he adventures into the strangely familiar, mysterious fantasy world, attempting to save all the heroes as well as himself, but his quest becomes a lot harder when he is in cahoots with a demon. Can his sole existence save all the heroes when the tide of chaos rises to the surface?