In 3 seconds, regression will commence. Choi Hyeongyeol is trapped in a loop where, at the stroke of midnight on the 15th, he regresses back to the previous day. He has been forced to repeat the same assignment 20 times, pushing him to the brink of insanity. Driven completely mad, he decides to commit an act of defiance, and ends up having a one-night stand with his university classmate, Lim Yeonjeong . And then, the next morning, he awakens to the dawn of the 15th—for the very first time... A man driven insane by an eternal time loop finds that a single, reckless night with his classmate might just be the key to breaking his curse.