In 1889, the world was in the era of the booming industrial revolution, and the countries were closely connected, and the distance between them was suddenly shortened. However, greed was still the mainstream, and the European powers plundered in Asia and Africa, and the shadow of war always loomed over the world. At the World Expo held in Paris, France that year, the 14-year-old boy Jean (Riko Hidaka) who loved inventions met Nadia (Shuno Takamori), a girl from the circus. The black hair, brown skin and mysterious temperament exuded by the whole body made Jean curious, and he soon got involved in a dispute with Nadia. Grantis, who loves gems, and his two men Tom and Hansen started to chase and intercept the sapphire worn on Nadia's chest. They didn't know at this time that the gem was hiding an amazing secret. In the following days, Jean and Nadia launched a series of great adventures around this gem... This film is adapted from the science fiction novels "Twenty Thousand Leagues Under the Sea" and "Mysterious Island".