Sinb, Moonbin and Chanwoo are bestfriend since they were 6 years old. Now they're already 18 years old, Sinb and Moonbin was studying at the same university while Chanwoo was continuing his studies abroad in Sydney. Since childhood, Sinb likes Moonbin but fear of their friendship be affected she does not express it. 

Everyday, Doyoung will write a letter to Jaehyun but Jaehyun will never read that letters. Why? Because Doyoung will never give all the letters that he wrote to Jaehyun.