Ken's place is conveniently located, just a 5-minute walk from Sasazuka Station. The station itself is only one stop away (5-10 min train ride) from Shinjuku Station, which is the biggest hub in Tokyo - you can actually go everywhere in Tokyo from Shinjuku.
The apartment building is situated in a nice and quite neighbourhood, a very comfortable and safe environment overall. You can find many shops, cafes, grocery stores, supermarkets and convenient stores along the way from the station to the apartment. There is a convenient store at the corner of the street where you access the neighbourhood; and I found it especially convenient to buy daily travel supplies: water, food & snacks, etc, for starting the day or coming back.
My friends and I loved the apartment. It's modern, clean, comfortable and also equipped with essential amenities. It is a very functional space for all traveling needs incl. cooking and doing the laundry. Especially for travellers from SE Asia, you will fall in love with the toilet, because we do have a special need (re: rear washer) when we do our private business. This is a plus point for us. Ken also provides a House Manual to explain all the different functions of the household electronics.
Overall, it's an excellent choice for couples traveling to Tokyo and also very comfortable for a family of four. There's actually nothing that made our stay less convenient, we had a very great stay. However, I need to remind travellers that in Japan, garbage sorting is a HUGE deal; so please read the disposal instructions carefully. :D