This is a convenient, clean, pleasant place to stay right in the middle of Shinjuku. There is lots of natural light, the beds and linens are pristine, the building is new and the neighborhood is safe and convenient. I would recommend this place highly.
The building is a bit tricky to find, but with GPS guiding you, it's nothing to worry about.
There is a generous supermarket about ten minutes' walk away, and plenty of smaller restaurants and convenience stores even closer. Nishi-shinjuku-go-chome Station is about five minutes' walk. I was able to leave my bags in a coin locker downstairs in the lobby for an hour while I walked around after checkout, which was very convenient.
Thank you, Jun!