Taku was very nice and friendly, and he was pretty responsive to questions.
The neighborhood is nice, quiet and residential, tucked away from the busy main road leading to Central Shinjuku, and there are plenty of small restaurants, cafes, and convenience stores nearby.
However, the place is a quite a walk from the heart of Shinjuku (about 30 minutes) and is a 6-7 minute walk from the Yotsuya-Sanchōme Station, which does provide relatively easy access to Shinjuku Station, Shinjuku, and the Yamanote line. You can also get to Central Tokyo pretty quickly from Yotsuya-Sanchōme.
My main issue with the house was that it was not very clean, and once you arrive it becomes clear that the pictures posted are rather old. Even for low prices, cleanliness should be a bare minimum. There was a lot of clutter in the bathroom and kitchen, and there was visible grime throughout. If the place is given a thorough cleaning and more attention is given to upkeep, it would make for a great stay.