National Parks of Japan
The Ministry of the Environment has published two brochures about the natural environment in Japan. The first is called “National Parks of Japan” and the second is the equally blandly named “The Nature of Japan”. They are both available in Chinese, English, Japanese, and Korean.
They are not particularly well written (they didn’t bother to have the translations checked by a native English speaker), but they may give you some ideas about where to travel to experience the natural beauty of the Japanese archipelago.