One day, Kandume's can boy, who happily lived with his friends in the kitchen, becomes an empty can and is discarded. Eventually, he has a dream about the history of iron and humanity. He sees how iron that melted and flowed out during a forest fire was discovered by humans once it cooled and solidified. This iron then transformed into knives and machines, leading to the development of civilization. When the can boy awakens, he is taken to a steelworks and reborn as a new steel material.