There are 118 volcanoes in Japan!
Japan has over 100 active volcanoes, more than almost any other country and accounts alone for about 10% of all active volcanoes in the world. 17 Japanese volcanoes had been documented in eruption, more than the rest of the world combined (including 10 in Europe).
Japan is a part of the Eurasia continent and made up of more than 6,000 islands. Also, it is formed on the volcanic line, called "Ring of Fire." (The regions of mountain-building earthquakes and volcanoes which surround the Pacific Ocean.)
Mount Aso is the largest active volcano in Japan, and is among the largest in the world and was Japan's first documented historical eruption in 553 AD; it holds a record in the number of historically documented eruptions.