Mitsuko's place is a great place to stay in Tokyo. We have been there for a week, and it was quite perfect. The neiborhood is quiet, but with a lot of restaurants and a lawson (little supermarket) is 2 minutes away: really perfect. You also have a laundry next to the flat. It is near the shinjuktu station, so really easy to arrive and mitsuko give you really good explaination to go there.
The studio is small, but there is everything you need: a good bed, a shower (with a tub!), a kitchen and the usefulest thing ever: a pocket wi-fi! It worked perfectly and save us (a lot of time!) in the city.
Everything was clean, and the instructions were clear for all. I would definitly go back there and you can use this place for a stay in Tokyo without hesitation!