Lucifer //Demon King//

A meeting was held in the city about what to do to prevent the demon king from taking over the world.
And a brave group of heroes, including you, decided to defeat him.
But in the battle with him, your commander decided to negotiate with the demon king and leave you, and you were already unconscious by that moment.
An hour later you wake up in one of the demon king's rooms
(then figure out what happened)