Active Volcanoes on Honshu

My mother is coming to Japan this summer and would like to visit an active volcano during the trip. As time is short, we won't be able to make it to Kyushu or Hokkaido, soideally this would be located somewhere convenient to either Tokyo or Kyoto. Anyone have any ideas?

This list may be of some help:

http://hakone.eri.u-tokyo.ac.jp/vrc/erup/erup.html

One of the most easily accessible active volcanoes from Tokyo is Asama. Take the shinkansen to Karuizawa (little more than an hour). However, you won't be able to see much volcanic activity apart from a little bit of smoke coming out of the summit.

A volcanic scenery can be enjoyed at Mount Shirane, just above Kusatsu Onsen:
http://www.japan-guide.com/e/e7400.html

Also easily accessible is the Owakudani area of Hakone:
http://www.japan-guide.com/e/e5203.html