Kazu's place is very conveniently located just 1-2 train stops from Shinjuku station. The house has 3 rooms on the 2nd floor that are occupied by guests as well as a shared bathroom on that floor (toilet area is separate). This can lead to some waiting for the bathroom but most of the time this was not an issue for me. This is a great place to stay for 1 person and I liked how convenient it was, and the fact that there was a grocery store nearby. There is no microwave so all cooking would be left to things you can make with hot water, but the fridge in the room was helpful to have.
I barely saw any of the other guests coming or going and Kazu and his sister were easily reachable should I need them. I would definitely stay here again and recommend this place to anyone looking for affordable, clean, quiet, no-frills place to stay while in Tokyo.