The Evil Warden and His Legendary Monster

On the surface, she is an ordinary silver-haired girl, but in truth she can transform into a monster feared by all. She is my familiar, the legendary Instrument of Sin, the Shackles of Inverse Providence. And I am her master, the evil warden known as the King of the Underworld, who commands the prison of the Myriad Worlds.

"Master, please enjoy me to your heart's content."

"Huh? You must be joking, right?"