I urge anyone thinking of Shinjuku to try Koichi-san's unit. The unit can accommodate my family of 4 (2children) comfortably. Here are the additional pros:
1. 10 mins walk from Metro train station.
2. 15 mins walk to the main shopping districts, including Shinjuku JR.
3. Super friendly and approachable host.
My only complain is there is no lift to the 2nd floor. However, there is only 1 flight of stairs. If needed, you can ask Koichi-san to help you.
My trip was made enjoyable with this unit. Well done l, Koichi-san!