As many reviewers mentioned, this hotel is located about 10 minutes away from the closest metro stop (Marunouchi Line - M10 (Shinjuku Gyoemmae)). The metro stop is small, but accessible to a number of tourist attractions. The hotel is also about a 15 minute walk to the heart of Shinjuku.
We loved our stay here; the onsen was a highlight after walking nearly 8-10 miles a day. We could relax, take a nice warm bath, and decompress from the tourist activities we had done that day.
Additionally, as many people mentioned too, the hotel is right across from 7-11, making it very easy to grab a quick bite to eat. Highly recommend doing the traditional Japanese breakfast at least ONCE during your stay at the hotel. It's beautifully presented and filling, but is just more costly than picking up a quick onigiri or sandwich from the 7-11.
There are laundry and water facilities on floors 5, 10 and 15. The onsen is located on floor 18, I believe. Our only complaint was that the rooms are just slightly tight. We had 2 adults, and one child, in a queen/king size bed futon, and we were hopping over our luggage and other things. It wasn't horribly inconvenient, but it was snug compared to other hotels we stayed at in Japan.
Overall, though, we enjoyed our stay here. My 8-yo daughter said it was "the best hotel we stayed at during our trip" so overall, we were pleased with the accommodation and overall ease of the hotel location and facilities. Thank you so much for a pleasant stay!