Jung-Suk (Jung Jae Young) is a librarian who is obsessive-compulsive and must set plans for everything like waking up at 6:00 AM and then arranging his bed by 6:35 AM. He also suffers from a fear of germs and always carries various disinfectants with him. Jung-Suk also has a secret crush on Ji-Won (Cha Ye-Ryun) who works at a convenience store near the library. Ji-Won also has obsessive–compulsive disorders like Jung-Suk.

Jung-Suk finally decides to reveal his feelings to Ji-Won by giving her a diary he has written in daily. To his surprise, Ji-Won is not working that day and a woman named So-Jung (Han Ji Min) is working there. Jung-Suk panics and leaves the store without his diary. Later, he goes back to get his diary and learns So-Jung will appear at a night club later that night. At the nightclub, Jung-Suk hears So-Jung sing a song called "Plan Man" which describes things he wrote in his diary. Soon, So-Jung asks Jung-Suk to take part in a TV music talent show.