Suggestions for something different for a one day trip to Tokyo?

I'll be in Japan for a few weeks soon. My wife has a Japanese friend who lives in Tokyo that we will be meeting for one day. This will be my wife's 6th time in Japan and I've lost count of how many times I've been there. I've done Tokyo to death and my wife has seen all the major sites (e.g., Meiji, Asakusa, museums, Shinjuku Gyoen, ...). Can anyone suggest something relaxing and not the usual tourist spot where we can relax with our Japanese friend (friend is in her late 40s and doesn't like to walk much - she lives near the "big egg"). Any unique neighborhood restaurants, unusual gardens, or other relaxed locations?

There are many laid-back spots that are not as famous or crowded in Tokyo, but I would like to suggest where I used to live.

The neighborhood around Azabu, Hiroo, Shirokane and Ebisu is quiet and relaxing. "Arisugawa Park" in Hiroo is a beautifully landscaped park with Metropolitan Library on the site. You will find Meidiya International supermarket which has a little bookstore on the second floor in front of the park entrance.
There are many, many shops and restaurants in this area that you wouldn't get bored.

I would say the area near the Azabu-Juban station would be nice. Nice little shops and sidewalk cafes there.

Did you visit here?
Tokyo metropolitan teien art museum
http://www.teien-art-museum.ne.jp/info/e_index.html
TOKYO Metropolitan Park Association
http://www.tokyo-park.or.jp/english/index.html
(teien, a botanical garden, a park, the prospects place) link in Tokyo
名所旧跡／庭園／植物園／公園／展望所：東京
Imperial Palace East Garden
http://www.kunaicho.go.jp/e17/ed17-05.html