The flat is ideally located and the host is so thoughtful. The place is clean and comfortable. For anyone thinking of staying here I would recommend to read the details. It is easy to get to the place using public transport. Get to Shinjuku Station from Narita or Heneda using the express train. Purchase a Suicca card (Train pass) is advance and use the Marunouchi Line(Tube/underground train) from station 8(Shinjuku) to station 11 (Yotsuya-sanchome). Take the exit 3 and turn left when you come out of the station. Walk along the road (Without crossing the lights) and take the second lane on the left (Samancho) which is next to the 7/11 shop. The house is on the left side after the road on the right. Almost facing the road on the right. Flat 301.
Note that the flat has a portable wifi router/power bank that can be taken with you once connected and will provide you wifi on the road as well as charge your phone.
Excellent place and recommend anyone to stay.