Beautifully clean apartment as shown in the photos, and centrally located in a very peaceful residential part of Shinjuku.
It's about 12 minutes to Kabukicho via the subway and 15 minutes to Shibuya (I'm using the Hotel Gracery and Mega Don Quixote as points of reference, respectively, using Google maps).
On a tangent, I'd suggest not coming to Tokyo until beginning of October. It was in the mid-80's in terms of temperature with high humidity, so the weather can feel oppressive. Fortunately, this location has pretty good AC, thank goodness.
One of the biggest benefits of booking this location is hands-down, the 2 minute walk to 7-11 just around the corner. That is golden for grabbing water and a quick breakfast in the morning. There's also a supermarket (Marusho) and a small pharmacy down the street adjacent to restaurant Saizeriya.
On another tangent: Yelp does work in Japan, but it appears to be still in its early stages of adoption as of the time of this writing, so reviews and locations listed are very limited. Your best bet is to use Google maps along with Google translate to find things that are needed. Reserving a pocket wi-fi at the post office inside Narita airport was absolutely essential for this trip (my friend and I did not use the one provided by Shin)
All in all, a good place to stay and get rest while visiting the Tokyo area.