Seiji's apartment is so comfortable and clean. He has thought of all the small things to make the stay pleasant. The bed was our favourite as we arrived very jet lagged and it was so comfortable and the duvet the perfect thickness. It was cold while we stayed in early March and we used the air con to heat the room up.
The bathroom is small but perfectly formed. It had all the soap, shampoos and toothbrushes for anyone who has forgotten anything.
It is very easy to get to from Shinjuku and the local station - we tended to walk the whole way.
Only note would be that we were travelling for 2 weeks and brought 2 weeks of clothes in large suitcases - it was a tight fit to have our suitcases in the flat but we fitted them in the hall way and next to the bed so we were still able to enjoy the apartment.