Mount Aso, Kumamoto Japan
Note that the crater area is often partially and sometimes completely closed off to visitors due to poisonous volcanic gases or the risk of volcanic activity. So, make sure to check the volcano's current statebefore traveling there. Even when the area around the summit is open, gases can be intense, and people with respiratory problems should refrain from approaching the crater.
Komezuka is a small, beautifully shaped volcanic cone on the northern slopes of Nakadake. There are pleasant walking trails in the vicinity (but not to the top) of Komezuka, however, easy access by public transportation is not provided.