Science ZERO utilizes cutting edge knowledge and technology to thoroughly investigate various phenomena from a scientific perspective. In this episode, we focus on Oze, Japan's largest mountain wetlands, where a comprehensive scientific survey was conducted after a hiatus of 20 years. Documenting the survey team for one year, this program joins them in revealing the secrets that have made Oze a paradise for rare flora and fauna. Even the experts are surprised by what they find in a pond called Ryugu Pond. How can this small pool possibly keep absorbing a stream of water that continually eddies in? Using the latest underwater drone technology, the survey team discovers a complex tunnel structure beneath the pond. It turns out that the key to Oze's unique ecosystem can be found in an unknown subterranean world!