Excellent, very walkable location near Shinjuku Goen, 5 min to the Marunochi subway line, 15 min to Shijnuku station. Lots of space, very quiet and great aesthetic.
Great restaurants nearby in the neighbourhood (try King Kong for Japanese BBG, and Chatty, Chatty for burgers and sandwiches) and many other options along Shinjuku-dori. We would definitely return to this our the hosts other apartments.