A love story and a story about relationships where the only world they share becomes a light that they still believe in and provides direction. Yeon Tae O is a train driver. He is a someone whose life changes after losing his parents in an accident in March, when he was nineteen and living in a small provincial city, and his younger brother Tae Seo, who was riding with him, gets injured in an accident. He expresses feelings of loneliness, longing, and pain as he meets Mo Eun A, whom he met when he was nineteen, and breaks up with her when he is twenty, but reunites with her when he is thirty. Mo Eun Ah is a hotelier. She first meets Tae O when she was nineteen and experiences changes in her work, relationships, and the direction of her life after reuniting with him in her thirties after ten years. (Source: Korean = Naver || Translation = MyDramaList)