Hyun Bin's girlfriend Bae suzy falls from hostel window and died. which leads him into a depressed state to which he finds a book on the road where he collapses. As he decides to burn all of his memories with his ex-girlfriend, He discovers the book he found on the road and begins to read it.
The book happens to be a diary that belonged to Kim-Ji won. Kim-Ji won is a strange woman who doesn't use a Mobile Phone, and believes in human interaction. Hyun Bin connects with the diary and develops feelings for the woman. Kim-Ji won visited shanghai to deliver a letter from her grandfather to a man named Victor. Through her journey of contacting him, she was attacked by anonymous people and was in deep trouble.
After 18 pages of reading, the diary happened to be empty and at first, he thought she stopped journalling since her task was completed. When he goes to meet her at her hometown, Hyun Bin discovers a shocking revelation from Kim-Ji won's grandmother that both Kim-Ji won and her friend Sophia died in a car accident a year prior.
Hyun Bin couldn't digest the fact that the woman he loved had died. Through the advice from his grandfather, he decides to complete her unattended tasks to make himself and everyone around feel that Kim-Ji won is alive. As he completes those tasks, he gets to know that Kim-Ji won may still be alive through a bus conductor who happened to see Kim-ji won in the ICU 2 days after she was believed to be dead.
To find more clues as to where Kim-Ji won is, Hyun Bin begins his search for the letter that was supposed to be passed to Victor. Hyun Bin finds out that an architect Talwar was trying to kill Kim Ji won for that cover as it contains proof to a case that he is being prosecuted against and hopes to destroy it.
Hyun Bin finally knows that Kim ji won is alive and well through Dr. Sudoko, who happens to know Kim ji won and is also Hyun Bin's neighbour. Hyun Bin decides to not meet her as he understands that she may not love him back.
Six months later, Kim Ji won returns to her regular life and is surprised to see all her tasks she hoped to complete before the accident accomplished by Hyun Bin. She ponders his identity and enquires with the bus conductor, Sudoko and Hyun Bin's best friend, Jasmine. She finds out that Hyun Bin will be going to Beijing to commemorate the death anniversary of Kim Ji won's parents. In hopes to find Hyun Bin, she unexpectedly bumps into him and reciprocates the feeling 'Love' back.
It is later revealed that in one of the tasks of Kim ji won, it was to buy a watch for an anonymous person who guarded her in a riot and broke his watch in the process. That person just so happened to be Hyun Bin.