Detectives from the present and a detective from the past communicate via walkie-talkie to solve a long-time unsolved case.

Yoo So Joon owns a real estate company worth 200 billion won. When he sees his future self living unhappily, he decides to avoid that fate by marrying Song Ma Rin without love. While their start is a fake marriage, he sees that his wife gets hurt because of him, and it starts to distress him. Slowly he will be falling in love with her, despite marrying her for selfish and loveless reasons.

A woman named Seo Ji-Woo (Im Soo-Jung) traveled to India and met her first true love Kim Jong-Ok. Since that time Ji-Woo can't forget her first love. She then turns the company "첫사랑 찾기 주식회사" - which means literally "Finding Your First True Love Company" to help track down Kim Jong-Ok. Han Gi-Joon (Gong Yoo) started "Finding Your First True Love Company" and he takes on Seo Ji-Woo is the company's first client. The pair travel all over Korea to find Seo Ji-Woo's first love and & in the process Han Gi-Joon falls in love with his first client ...

When Seung Min was on his first year at the Academy of Architecture, he met Seo Yeon. She was a musician student, and Seung Min totally fell in love with her. Years have passed, and now he meets Seo Yeon again - she asks him to rebuild her father's old house.