In the wake of Japan's bubble economy collapse, a stagnant and oppressive atmosphere hangs over a rural northern town. In this setting lives a young boy named Tōma, weighed down by a harsh home life. His father is an alcoholic, frequently driving Tōma out of the house, forcing the boy to seek refuge elsewhere. Tōma has built a secret base in a nearby forest, a place that serves as his only sanctuary. One day in that hideaway, he discovers a mysterious egg. He carefully tends to it, eagerly waiting for it to hatch. Several days later, what emerges is a small, black, bird-like creature of unknown origin. Tōma names this enigmatic being and begins to form a bond with it, clinging to the idea that they will be friends forever. This encounter sets in motion a chain of events that profoundly alters the course of Tōma's life, as his connection with the creature deepens into an unsettling and fateful relationship that blurs the lines between companionship, dependency, and something far more sinister. The story explores themes of loneliness, fractured family dynamics, and the desperate need for connection, all set against the bleak backdrop of a decaying rural community.