Me and my husband stayed for 2 month in Koichi's place. The location is very convenient nearby the Nishishinjuku Gochome station, nearby there's everything you need on a daily basis (restaurants, shops, pharmacies, coffeeshops and so on).
Koichi also provided detailed and useful informations throughout our stay, always answering my questions.
The room itself is renewed, comfortable and well equipped with everything you may need for a short and medium stay. Everything is exactly as advertised.
The neighborhood is quiet and safe. I highly recommend it.