Three of my friends and I went to Tokyo for a week, and we decided to stay at Koichi's place. There was plenty of room for the four of us, plus our luggage. Koichi was very hospitable and even picked us up from the subway station when we arrived late at night. The location itself is less than a ten minute walk to the main Shinjuku street, plus different subway stations.
If I ever travel back to Japan and stay in Tokyo, I will definitely try to stay at Koichi's Airbnb!