One Day 2017 Insurance examiner Gang Soo Kim Nam Gil falls into a deep depression in the wake of the death of his beloved wife As he returns to work, he takes on the case of Mi So Chun Woo Hee whom is laying in a coma in the hospital Gang Soo meets a woman there who introduce herself as Mi So, and it turns out that he is the only one capable of seeing her It turns out that Mi So has been in a terrible car accident and while her body is deep in a coma, her spirit is roaming free And Mi So has something that she needs Gang Soo to do for her