This appartment suited me almost perfectly. Very close to nishishinjuku gochome station (5min walk) and two stops from Shinjuku station. Flat was clean, good wifi, and key was hanging from the door, all I had to do was enter the code.
I had problems contacting Kazumi because Japanese numbers worked with +81 but not 0081 from my mobile! Luckily the "Family Mart" supermarket just next to the go-chome station had free wifi and I managed to email Kazumi. He replied really quickly and got a friend to ring me back who spoke good English to confirm we'd understood each other - thanks Kazumi. Once I had the key everything was easy. The flat's in an attractive side street and people were very helpful and friendly. I said "almost" perfect because my friends were staying in roppongi so getting home after the metro closes was a bit costly (taxi about 40€), but this has nothing to do with Kazumi's flat. Many thanks!