We were very happy with our stay here. The location is great! Very convenient to the cool Shinjuku area, but down a quiet alley so the noise of the city won't bother you too much. The host sent us pictorial instructions on getting to the space that were very helpful.
While the space is small by American standards, it was perfect for two people who want to spend most of their time out exploring the city. Great bathroom/shower area, and even a clothes washer (though like in many Japanese homes there is no dryer, so if you use it, make sure you give your clothes enough time to hang dry - there is a hanging bar on the little balcony for this purpose).
The space was very clean. The host provides house slippers and there's a small fridge, a stovetop, a hot water kettle, and a few dishes and utensils for use. We were also welcomed with snacks and candy which was a nice touch!
There's a cute Shiba Inu who lives outside in a little doghouse, we loved seeing him on our arrival and departure each time.
We would definitely stay here again and actually preferred it to a more expensive hotel we stayed in later in our trip!