Sunmall Crest607 is studio apartment located in luxurious building, perfectly situated near all the bars and clubs of Shinjuku NiChome. The apartment's bathroom was the most comfortable of all the locations we stayed at for this trip (traveling through Japan as a westerner, you'll understand). Though there were other appreciable amenities such as a full kitchen, fridge, washer, and living room - we stayed out the entire trip and did not take advantage of any of them.
If you want a great place to lay your head comfortably between partying in Shinjuku, I highly recommend this location.