Fourteen-year-old girl Saito Akari (played by Mayuko Fukuda) adopted a cute puppy. At her mother's suggestion, she named the puppy "Sox" and made "ten promises" with the puppy. Soon, her mother died, and her father, a doctor, was busy with work and had no time to take care of Akari, so "Sox" became Akari's most loyal playmate. Akari also had a friend Xingjin at school who dreamed of becoming a performer. When Akari moved because of her father's job transfer, "Sox" was fostered in Xingjin's home. But when Xingjin (played by Shota Sato) was going to study abroad, his father did not send him on time because of an emergency, and Akari was unable to see Xingjin for the last time. In order to make up for his long-term debt to his daughter, his father decided to resign and open a small clinic, and the "family of three" lived together again. After growing up, Akari began a busy life, and she spent less and less time with "Sox" and her father. Later, Akari (played by Rena Tanaka) met Xingjin (played by Ryo Kase) who had returned from school, and the two became lovers. Soon, ten years had passed since she first met Suokes, and Suokes also came to the end of his life. At this time, Mingli remembered the ten promises she had made with Suokes...