She is in elementary school and he is in junior high school. She is in junior high school and he is in high school. She is in high school and he is in college. She chose his school without looking back. She caught up with him, but he wanted to go abroad. Life goes on without him. Studying, eating, sleeping, why is my heart always empty? She didn't know how wonderful the outside world was, but she was still waiting for his return. All his friends asked him. How good is he? She couldn't answer, until she heard a line of lyrics. Some people couldn't tell what was good about it, but no one could replace it. It turned out that years of following made her understand. He has long been an irreplaceable part of her heart. I heard that he is back, will they find their past again?