It was the primitive age. One day, Toto who lived in a cave, found a strange shaped horn. Whose horn is it? Toto went to the woods to look for its owner, but nobody had ever seen a horn of such unusual shape. Toto asked the ancestor of the big-horned rhinoceros, but Arsinoterium, the ancestor, disturbed in his sleep, became angry and chased Toto. Toto was at a complete loss, holding a horn nobody seemed to have lost, when his father came running up to him and said, "This is a tool for drawing pictures. I made it for you." As a matter of fact, it turned out to be a G-pen (a pen used for drawing cartoons) made of stone.
Rock paintings from the primitive age have been found on the walls of caves. These include fine drawings of animals and of daily human activities. Tezuka Osamu, being a professional cartoonist, saw these drawings and wondered what kind of tool had been used. Maybe an inventor in ancient times had come up with the idea of a G-pen... Tezuka Osamu certainly didn't lack imagination to associate the tool he used everyday with the cave paintings. Because he wonders what kind of tool can produce such wonderful drawings, Tezuka Osamu demonstrates his individuality here in that, "calm observation can create a big leap in imagination".