A documentary exploring the ecology of migratory birds that fly to the Tono region of Gifu Prefecture. Director Imai Tomoki is told by his grandfather Teruo that the sky in his hometown was once filled with a massive flock of migratory birds. At that time, 'mist net hunting' was carried out in the village. How were birds caught? Why was it necessary to eat migratory birds? And why is such hunting now banned? Imai diligently seeks the answers to each of these questions that arise on his quest to find the bird's migratory path.