Chisako Satoya, a writer, and her father, Kozo, had a long-standing feud and had been living apart for a long time. However now that Kozo, who lives alone, has dementia, so she returns to her hometown to begin taking care of him. One day, she rescues a boy who has lost his memory in an accident and has signs of abuse on his body. To protect him, she pretends about being his mother and starts living with the boy. Is this lie a sin or love?