The Havira are a race of tiny, humanoid butterfly people discovered on the Amami Islands, facing extinction due to natural predators and human development. Humans have taken control of their survival, establishing protected areas where the Havira live in a state of dependent care. To manage their population, humans enforce a breeding program, selecting tsugai, or mating pairs, for each generation without regard for the individuals own desires.

The story follows a young Havira named Oshino and his assigned mate, Mai. They live in a partitioned section of a human facility, navigating a world where even simple furniture presents a massive obstacle course. Their lives are managed by Omura, a low-ranking human director who views them as specimens under his care. Despite living together in a repurposed car, Oshino struggles to connect with Mai, who seems distant and whose affections lie elsewhere, particularly with a confident and knowledgeable young woman named Oki-san. Oki-san dreams of returning to their natural habitat, arguing that freedom is worth the risk of losing human protection.

The fragile peace of the sanctuary is shattered when crows, terrifying natural predators, break into their enclosure. The attack is sudden and brutal, resulting in the death of a young Havira. In the chaos, Oshino heroically sacrifices himself to save Mai from a crow, gouging out its eye as it carries him away. This event marks a pivotal turning point, shattering the false security of the protected area. It ignites the Havira uprising, forcing the surviving residents to confront the harsh reality of their world and fight for their freedom from human control.