This song is about a girl who fell in love with her best friend in college. They started as friends but the boy has a girlfriend so the girl could only stay at his side but can never tell her true feelings for him. He was her first love.
When the boy broke up with his girlfriend, he couldn't move on from the thought of his former girlfriend even if his best friend had always been there for him. She felt hurt because he never saw her more than as a friend.
When they graduated, they had their own lives. The girl realized the pain of being apart from him, that they will never be lovers. She wishes that he will realize how much she loves him and how much that love hurts her.