Silver Demon King

Silver Demon King summary:

【Translation provided by the copyright owner.】Yooan Ha, a high school senior, messed up his finals because he mismarked his papers. He is approached by a foreigner- no, a demon who proposes to turn back time. In exchange, Yooan must stand in as the demon king's replacement...Will Yooan, living the demon king's life, be able to safely return to his own life?“Should I live however I want? I'm the real king until the real one returns!”