Yun-lee is a girl carrying a deep emotional scar in her heart. Because of an accident, she lost two precious years of her life—the period between ages 19 and 21. Her life feels empty. She is miserable, yet she continues attending preparatory school in an effort to make up for the time she has lost. One day, while on her way to feed stray cats, she encounters a young man who appears to possess what she has lost: the years between 19 and 21.