After a lifetime of bloodshed, the Heavenly Demon longs for peace. In his final moments, he uncovers the truth about his power and yearns for a different life. He wakes up in the body of Taesan Byeok, the frail second son of a powerful merchant family, barely clinging to life. Using his knowledge from his life as the Heavenly Demon, Taesan must navigate a world of temptation and corruption to survive. As his martial arts reputation grows, new enemies emerge to disrupt his quiet life. Yet, Taesan is determined to live on his own terms, despite the chaos around him.