Satoru is afflicted with insomnia and is confined to his own nocturnal realm, detached from the world's incessant rotation. His fate alters as he chances upon Mikoto, an atypical individual with the capacity to perceive in the absence of light but suffers sightlessness in daylight. Mikoto has enlisted his assistance to find a picture book she had previously perused. The job appears simple, but the task evolves into a one-of-a-kind escapade for the duo.