We stayed in a private apartment in Norimasa's building, which is located on the edge of the bar and restaurant district in Nakano. That being said, the apartment is located on the first floor above several restaurants and bars, which obviously causes noise during evening and night.
Hence, I do not recommend the flat if you are sensitive to noise. We enjoyed our stay, however, as we live in similar district back home and did just fine, even though we were travelling with a 10-month old baby. The apartment itself is clean and spacious with a tatami and a balcony. There is also a cheap washing machine (200 yen, detergent included) in the premises.
The host is a friendly person and extremely helpful, and obviously dedicated to his guests.