I really enjoyed my stay at Sayaka's place! The location is excellent - just 5 or so minutes away from Shinjuku-Sanchome. There are a lot of convenience stores and a big supermarket nearby, so you won't lack for anything.
The house comes equipped with everything you need for an extended stay, and the self-check-in system works well.
The bedroom floor is actually tatami (would have looked way better if it were out in the open), so the room is very comfortable. I would say this is a good place for a couple, but there is also a small sofa and a futon for extra guests.
Overall, I had a great time there and would definitely book again!