Set in the early 20th century, Kokoro opens with a chance encounter on a beach near Tokyo that irrevocably links a young student to a man he simply calls Sensei (Teacher). Intrigued by Sensei's aloofness, the student calls upon him with increasing frequency. Eventually, Sensei and his beautiful wife open their home and their lives to him. Only later does the student learn the devastating secret that has haunted Sensei since his youth.