Sulli is an orphan, so for her the word "Family" is as unknown as important, She is a strange girl who has troubles making friends, because of her strange personality She suffers bulling, nevertheless her life seems to begin to shine because she finally seems to fulfill her dream of becoming a singer, now for her the most important thing is the future and never to think about the past. By contrast, Minho has amnesia and is obsessed with the past, he always takes his camera with him and every day he search in different photos that he took before losing memory to see if there is something to help him recover his memory. When Sulli and Minho coincide in the same class in college, he is sure that this girl knows something about  his past while Sulli is curious about if that guy will have some role in her future.

The only problem is that they have a time limit to remember each other.