One of the characteristics of Japan’s natural environment is the abundance of water springs. Various animals have evolved to adapt to this aquatic environment, resulting in unique species found only in Japan. One example is Tago’s brown frog, which is being studied by Dr. Koshiro Eto. Generally called “common frogs,” brown frogs are the most well-known frog group and are found widely in the northern hemisphere. Most of them live in still water, such as ponds. However, Tago’s brown frog differs from others of the same genus as it breeds in the unique water spring environment. According to my research, it is only in Japan that this unique ecological character has evolved from the ordinary still water species. Tago’s brown frog is a common species, abundant in Japanese mountains, but it is actually quite a remarkable expression of Japan’s unique natural environment.