According to the Japan Meteorological Agency, Japan has 108 active volcanoes.
#1.Mt. Fuji is an active volcano about 100 kilometers southwest of Tokyo and highest and most iconic landmark in Japan. Mount Fuji has erupted at least 16 times since 781 AD and the eruptions are typically violent. A popular place for viewing Mt. Fuji is Tenjo-Yama Park where a cable car takes visitors 1,000 meter up to the viewing platform.
#2.Mount Aso or Aso-san is the largest active volcano in Japan, which lies almost in the center of the island of Honshu. It consists of five separate volcanic peaks, one of which is still active and regularly emits volcanic smoke. For a hefty price people can take quick helicopter trips or drive up to the summit of the crater
#3.Sakurajima is a volcanic island, which floats in the sea only 4km from South Kyushu’s hub city, Kagoshima. It consists of three volcanoes, one of which is still active and regularly dumps ash on the city below. It stands 1,117 meters tall and 50km round. A popular place for viewing Sakurajima volcano is Yunohira Lookout which is a two hour hike or 15 minutes drive from Sakurajima harbor.
#4.Mount Asama stands 2,568 metres (8,425 ft) above sea level towering over beautiful mountain resort town of Karuizawa. It is the most active volcano of Honshu and one of the volcanoes with the longest recorded history of documented eruptions. Mount Asama had a major eruption in 1783 that resulted in national famine that lasted 4-5 years. Hot Springs has been popular tourist spot.
#5.Mount Unzen is a large complex volcano made of several adjacent and overlapping lava domes, near the city of Shimabara. Today the volcano is regarded as dormant. Visitors can climb the 1,359 meter peak to enjoy panoramic views or shorten the trek from Mount Myoken, which is reached by a three-minute gondola ride from Nita Pass.Source