Prison Town is a place that holds incarcerated monsters as they work towards reducing their sentences. However, one day, a human named Akari Sakuragi ends up serving time after falling asleep on a train. Accused of trespassing, she is given a sentence and must work alongside the monsters to earn her freedom. One condition of the town is that every inhabitant must live with a partner as it is believed this helps to motivate the prisoners.

Akari is assigned to Mary, a man-made creature with a reserved demeanor. While Mary is referred to as a workaholic by most, Akari struggles to adapt to the abnormal jobs she is required to do: the two women could not be more different from each other. Yet, as she spends more time with her, Akari finds herself wanting to know more about Mary regardless of their differences. But how will Akari react when she discovers the reason why Mary was sentenced to work in Prison Town?