Growing up as an orphan, Jeong He-Jin didn’t open his heart to anyone. After giving his all to become a cardiothoracic surgeon, he got into an unfortunate accident, after which he woke up not as ‘Jeon He-Jin’ but as ‘Choi GiSeok’. And on top of that, he has to <Level Up> using his skills…? The accident changed his fate drastically… Can he become ‘the Greatest Cardiothoracic Surgeon’ as ‘Choi GiSeok’?