I don't want to leave you but I can't stay here any longer. I'm sorry I broke our promise. I hope we'll meet again someday, but for now, please stay strong for me.

Shin HeeYoung and Beat have been dating since they're in High School and people always sees them as the perfect couple. It's almost their 4 years being together when something change in HeeYoung. She became weaker and always keep her distance with Beat everytime they met. Beat is curious and determined to find out about his girlfriend, but when he did found out the truth, he wish he never know what's she's been hiding.