The story of two orphan kids who grew up together, together they feel like family. Their bond became the purest form of love between them. Because of the immense love and innocence 8 years old Y/N asks her best friend Park Jimin to promise her that he would marry her. Due to the tenderness of the age he accepted her proposal. But with age the bond changed so changed the interest, after 5 years when Park Jimin again met Y/N he surprised her with a girlfriend. What will happen to Y/N? Will Y/N accept the fact that her best friend broke their childhood promise.