Monitoring activity of active volcanoes
In 2014, Mt. Ontake erupted suddenly killing many hikers.
In 2016, Mt. Aso erupted and many local people suffered heavy losses in the eruptions.
Japan is made up of volcanic islands. there are many active volcanoes in Japan. You may be an eruption victim someday if you hike a mountain with a warning of an eruption.
A total of 110 active volcanoes are monitored by the agency and Volcanic Warnings are issued by the Japan Meteorological Agency in relation to expected volcanic disasters, and identify potentially affected areas. Current Volcanic Warnings are presented in both Japanese and English (an example is attached below). If you plan to hike Japanese mountains, I do recommend to check the following websites.
Example of volcanic warnings