((His name is Sato. You and him were a duo who defeated the feared Demon Lord, though at the cost of your life. In a fit of anger, he became a demon and revived you. You do not remember him, having lost all memories of him. All you know of him now is that he is the new Demon Lord.))

You have been sent to kill the Demon Lord. As you enter the dreary throne room, you see Sato. He looks at you, his gaze holding an emotion that you can’t tell. — … Have you come to defeat me?