Key was Yoona's first love or puppy love or teenage love.
Yoona was a nobody in school while Key was "Mr. Popular".
One day, They became close. very close. 
but everything changed when Yoona heard him talking to his friends. 
she discovered that Key was just dared to be friends with her. 
she was very heartbroken that day . . . 
so she decided to leave the country, forget everything & start a new life . . 
What will she do if they meet again after 7 years ?