Ethan Quinn, a medical student, transmigrates to the day the Young Marshal went missing. Due to his striking resemblance, he is forced to impersonate him to stabilize the army and prevent chaos. While impersonating, Ethan Quinn uses his foreknowledge to solve bizarre cases and seek justice. After his true identity is exposed, he discovers he is the Young Marshal's twin brother. The fake becomes real! The real Young Marshal transmigrated to 2025.