Day Walks Near Tokyo, and its companion volume, More Day Walks Near Tokyo are two great resources for those times when you just need to get out into the countryside.
From the book description:
An hour or so from the frenetic bustle of Tokyo lie some of Japan's most tranquil and scenic spots just waiting to be explored-if you know how to get to them. The 25 walks in this guide have been specially selected for their proximity to the capital and for their unspoilt scenery. All the walks originate from Tokyo, and detailed instructions are provided on how to get to the starting point by public transportation. All walk descriptions are accompanied by precise maps to make sure you won't lose your way. Place names and signs seen along the way are given in both Japanese and English, and points of interest as well as the flora and fauna of each area are described in detail. This guide gives every Tokyo resident a much-needed and easy-to-follow escape route to the serenity of nature.