The River of Purgatory was a barren planet, and crops often grew with great difficulty. Almost all of the pioneers sent to the planet either died or left. Gombei and Yosaku, father and son, were the only two left on the planet. While Gombei kept on ploughing the field, believing that one day his hard work would prevail, Yosaku wanted to leave the planet. A giant bird flew to Gombei's field and picked Gombei's crops. Though Tetsuro managed to chase it away, it came back and started eating off Yosaku's field. Gombei tried to drive it off but was injured. Seeing this, Yosaku came to his father's defense. Tetsuro gave the fatal blow to the bird, and Yosaku, decided to remain on the planet, and worked the land until it became fertile.
Sur Limbo, une planète sans herbe ni arbres, Tetsuro et Maetel rencontrent un homme vivant une vie difficile à labourer le sol dans de telles conditions difficiles, et son fils, Yosaku. Ils prévoient de labourer le sol jusqu'à ce que les récoltes soient mûres, mais un oiseau monstrueux les attaque. Pour le protéger, Tetsuro et Yosaku combattent l'oiseau...
