Silver Devil King

Yooan Ha, a senior in high school, failed the SATs that were deemed as the "most effortless" as he filled in the scantron inaccurately. While pondering on his future by the Han River, a demon approaches him and proposes to rewind time. However, the demon king demands Yooan's appearance in his domain in exchange for the request. Can Yooan guarantee his reversion to his real life after fulfilling the demon king's requirement?