based on the Japanese novel published in 2002, Mr. Tsubakiyama's Seven Days by Jiro Asada
Kim Young-soo (Kim In-kwon) is a section chief in the womens apparel section at Sunjin's department store. He and his wife Shin Da-hye (Lee Min-jung) do not get along because his long work hours and constant overtime distract him from home. During one of these overtimes, he accidentally falls from a roof and is killed. His company writes his death off as a suicide in order to not receive blame for overworking him.
Han Gi-tak (Kim Soo-ro) is a former gangster who runs a restaurant. He has loved actress Song Yi-yeon (Lee Ha-nui) for many years, but she has always distanced herself from him because of his lifestyle. Her ex-husband, Cha Jae-gook (Choi Won-young) has whipped up a scandal to force her to give him their child, and threatens Yi-yeon with it. Just as Gi-tak figures this out, he gets in a car accident and is killed at the same time as Young-soo.
Young-soo and Gi-tak both arrive in the afterlife, but they both feel that they must return: Young-soo to reconcile with his wife and prove his death was not a suicide, and Gi-tak to protect Yi-yeon. They are given two months and return to life in new bodies: Young-soo as Lee Hae-joon (Rain), a handsome young man; and Gi-tak as Han Hong-nan (Oh Yeon-seo), a pretty young woman.
They have three rules:
1. They can not reveal their true identities.
2. Revenge is forbidden.
3. They can not engage in human affairs.
If they break any of these 3 rules, they will face terrible consequences.