Choi Kang-Woo is a former detective, but he now works as a veteran insurance investigator. He leads a team that attempts to reveal insurance fraud cases.

It is a love story of Han Se-gye (Seo Hyun-jin) who is an A-list actress. She is known as a troublemaker and the object of many rumors. Her life is a mystery, but, in reality, she suffers from an unusual phenomenon. At a certain point every month, her appearance changes to a different person. She lives one week out of every month with a different appearance, and Seo Do-jae (Lee Min-ki) who is an executive director of an airline company. He seems perfect with an attractive appearance and intelligence but, he suffers from prosopagnosia. He hides this disability and tries hard to memorize people by their habits and mannerisms. The only face that he is able to recognize is Han Se-gye’s.

University students Yoon Jin-Myung, Jung Ye-Eun, Song Ji-Won, Kang Yi-Na and Yoo Eun-Jae share a house. Jin-Myung is busy supporting herself financially and studying. She suffers from lack of sleep. Ye-Eun is devoted to her boyfriend, she is clear about what she likes or not. Ji-Won has a bright personality and likes to drink. Yi-Na is popular due to her beautiful appearance. Eun-Jae is timid, but she has an unique taste for men.

Ahn Joong-Hee is an actor who used to be a member of an idol group. One day, he appears in front of a family who consists Byun Han-Soo and Na Young-Sil and their 4 children including Hye-Young and Mi-Young. Joong-Hee begins to live wth them.

Whenever elementary school teacher Kang Joon-soo (Lee Seung-gi) falls in love, he always gives too much of himself to the relationship. Yet despite that, he ends up being the one getting dumped by his girlfriends. Joon-soo has been friends for 18 years with Kim Hyun-woo (Moon Chae-won), a weather forecaster whose beauty belies her witty tongue and aggressive manner.