Hot Springs I'm considering.

Hakone Onsen

 Easily reached from Tokyo and one of Japan's most popular hot spring resorts, Hakone boasts a large number of hot springs in beautiful setting along the forested valley and the shores of Lake Ashinoko.

 Arima Onsen  

Located still within the city limits of Kobe and just an hour outside of central Osaka, Arima Onsen is one of the Kansai Region's most popular hot spring resorts. It is also one of its oldest.

 Kurokawa Onsen

 Kurokawa Onsen is one of Japan's best hot spring resorts, both in terms of its pretty, traditional town center and its outstanding outdoor baths.