Thirty-five-year-old novelist Makio Koudai never had a good relationship with her older sister Minori, who constantly criticized her for being different. Because of this, Makio feels no grief upon hearing that Minori and her husband have died in a car crash. However, when Makio is asked to identify their bodies, she encounters her fifteen-year-old niece, Asa Takumi, whom she has not seen in years. As Asa struggles to process her parents' death, Makio reassures her that her complicated feelings are valid and suggests that the teenager start writing in a diary to cope with the loss. Upon learning that no other relatives want to take in Asa, Makio decides to become her guardian despite her lack of experience. In a world full of uncertainty, the novelist and the teenager must learn to live together while figuring themselves out.