Beyond the solar system, there is a small planet where a young boy named Robo lives. He hoped that his wish for a friend would come to pass with every day that goes by.
One day a mysterious rabbit humanoid, Usakichi, falls from the sky. Usakichi is a fugitive on the run from the army and befriends Robo to get a spaceship. However, the army catches up with Usakichi. Wanting to protect his first friend, Robo uses the item that his late father forbade him to use. After saving his Usakichi, Robo finds out that this item has the power to destroy planets.