Japan
 

We are planning a trip to Japan for 1 week and want to experience all the nature items, not really interested in exploring too much of city life. Is 1 week practical or do we need more time?

To experience "all the nature items" you would, of course, need MUCH more than a week. Whether a week would suit your interests is another matter entirely.
Here's a good place to start your research:
https://www.japan-guide.com/e/e2122.html