Oh Ha Rin (Yeri) is a 28-year-old woman whose heart still yearns for her first love and closest friend Ji Seo Jun (Hongseok). They were once as close …
What Ha Rin received for her 18th birthday was the death of her first love. 10 years have passed since. One day, when she visits her old neighborhood and retrieves Seo Jun's old photos. Since the photos remind her of the pain, she burns one of them.
When Ha Rin realizes that she had traveled back in time, she looks for Seo Jun. The dreamlike reunion only lasted for so short and she is back to the present. She thinks it was a dream, but soon notices that new memories from the past had been formed.
Ha Rin decides to find out why Seo Jun had committed suicide 10 years ago. She checks what kind of books Seo Jun had rented, reaches out to his friends, and also looks through his social media accounts. In the process, she discovers a shocking truth.
Ha Rin makes up her mind to prevent Seo Jun's death. She goes back to the past to resolve the conflict Seo Jun had with his mother. Although she succeeds, she remembers that she had forgotten the plans she had made with Su Jin, her best friend.
Having fixed the past, Ha Rin enjoys her date with 28-year-old Seo Jun, but she and Su Jin were not on good terms. She also finds out that Seo Jun's older sister Hye Min had passed away. She realizes that someone has to pay for the changes.
Ha Rin manages to save Hye Min from her death. But now that Hye Min is alive, Seo Jun is once again gone. Ha Rin tracks down the clues to Seo Jun's death, and notices some weird things. Once again, she burns another photo to find out the truth.
