Isuma Ito has always wondered what it was like to fly from the moment he saw a dazzling bird soar through the sky for the first time. He lives with the Sato family, one who will always be indebted to him and his family, along with their son Chikyuu Sato. Even though they have lived together since they were four, Isuma has never spoken a word. Chikyuu wants to save Isuma from his fate, but he doesn't want to be saved. Will Chikyuu persevere? What will they become?