Chapters 3 through 12 of the light novel follow the journey of Ai, a wingless angel, and Dia, a demon sealed within a rabbit plush toy. Their primary mission is to help lingering spirits find peace by fulfilling their final wishes, often referred to as making their "unfulfilled flowers bloom." Ai is searching for something she lost, which drives her to travel and meet people.
Their journey begins in a town where they stop at a cafe. Ai, despite being an angel who doesn't need to eat, enjoys a pancake, much to Dia's exasperation. Their conversation reveals their contrasting personalities: Ai is cheerful and prone to distractions, while Dia is more pragmatic and often exasperated by her behavior. Ai's desire for a moment of normalcy and connection, inspired by seeing other young people enjoying themselves, leads to this brief respite. Dia, though outwardly annoyed, shows a gentler side by wiping sauce from Ai's face, which melts her momentary frustration.
Later, Ai notices a young girl, seemingly younger than ten, who is ignored by everyone around her. The girl is asking people to read to her, but no one acknowledges her presence. Ai recognizes this as a situation where she might be able to help, but Dia intervenes, stating it's outside her jurisdiction as the girl is not a lingering spirit but a living soul. The girl then disappears.
Several days later, Ai and Dia are in an old house where they meet an elderly woman. Ai helps her carry groceries, and in return, the woman offers them tea and sweets. Ai, curious about the woman's life, notices her extensive collection of picture books, which are from her son, a picture book author. Ai chooses one with an angel illustration, intending to have Dia read it to her, as she struggles with reading. As they spend time together, enjoying the spring scenery, Dia senses a deathly presence.
Dia's ability to sense the dying allows them to move on. Ai bids farewell to the elderly woman, who expresses her gratitude for the company. As they leave, Dia points out a "lie" he sensed, implying the elderly woman was not the one who was dying. Ai, initially angered, quickly accepts this and they continue their journey.
Their travels lead them to observe the world around them, including an airplane, which Ai notes is a way for wingless humans to experience flight. Ai expresses her contentment with walking, as it allows her to see things she would miss from above. She again asks Dia to read the picture book, but he refuses, leading to a familiar back-and-forth. Ai recalls the incident with the ignored girl in the cafe and decides they must return to that town to read to her, believing it's important for the girl to have someone read to her. Dia, though seemingly resigned, agrees.
The narrative then shifts to a girl named Reina, who had been in a coma after a car accident. Her soul had been searching for someone to read her favorite picture book. Ai and Dia were led to her by Dia's ability to sense the dying. Reina's soul had been "wandering" and seeking comfort. Ai, mistaking Reina's soul for a lingering spirit, read her a different picture book. Reina, upon waking, exchanges the book Ai read with her own favorite, "The Sleeping Princess," and thanks Ai. Ai and Dia then leave before medical staff arrive.
The final chapters reveal that Ai's mission is to find the reason for her own "loneliness," stemming from a past sin and punishment, and Dia has his own secrets. They are also involved in helping those who have died, like Reina, and those who are still alive but in difficult circumstances, such as the girl in the hospital. The story concludes with Ai and Dia continuing their journey, encountering various people and situations, with Ai's free spirit guiding their path.