The flat is located in an off beaten path in Shinjuku, this tiny hidden neighborhood is really cute and filled with cool bars and restaurant where only locals go! This is clearly a premium location in Tokyo, gives you access to every major district easily and all big streets around Shinjuku.
Metro station is at 2mn by foot and several convenient stores are open 24/24h.
The flat was very clean, all was very well explained (manual).
The only observation I have, is how bright the room can get during the night because of the streetlights : I suggest the host add a thicker curtain on the window in front of the bed, I’m pretty sensitive to luminosity when it’s about sleeping and I needed an Eye mask. This being said, my girl friend slept like a baby.
Moreover, streets can be loud as it’s Tokyo - ear plugs are always a good option.
To conclude : My girlfriend and I really liked the stay and would totally come back/ suggest it to any couple who wants to experience Shinjuku and its surroundings.