This is a very convenient place to stay (really close to the Tokyo subway, and one stop away from the JR Shinjuku).
Kazumi proved to be a great host, and was very quick and responsive when we asked questions. There was a little bit of a mixup when we first arrived (we didn't know there was a code to get the key to the apartment), and Kazumi was very quick to respond and help us out. He also provided us chocolates to apologize :)
Overall, a good place to start when touring around Tokyo.