Visit Kyushu
The Official Kyushu Travel Guide

Mt. Aso in Aso-Kuju National Park, central Kyushu, is Japan's most active volcano. The huge caldera stretches 24 kilometers from north to south, surrounded by five peaks, known collectively as Aso Gogaku. Individually, they are Mt. Naka, Mt. Neko, Mt.Taka, Mt. Eboshi, and Mt. Kishima. Mt.Naka, with a milky green lake wreathed in smoke, is the most active peak, and the main attraction in the region. After the 2016 Kumamoto Earthquake, access to Mt. Naka was temporarily restricted, but the tourist route is now open again. It is a rare opportunity to seeing an active volcano up close. However, approaching the crater isn't permitted when it is particularly active. You can find real-time updates in English at http://www.aso.ne.jp/~volcano/eng/.