Ai has been looking for her daughter Miwa, who disappeared 24 years ago, leaving her infant daughter in Ai's care. One day she meets a woman in possession of Miwa's maternity passbook. However, the woman, who calls herself Masako, is afflicted by amnesia, and after 24 years, Ai is not able to judge whether the woman is her daughter or not. Masako recommends conducting a DNA analysis, but Ai rejects her offer and suggests they live together as a family. However, Ai's granddaughter Natsuki, whom Masako left to in Ai's care all those years earlier, is not able to hide her confusion at Masako's sudden arrival.