We stayed at Seiji's place for a business trip since our office is in Shinjuku. Location is great for both business and sightseeing since the place is very close to Shinjuku-Sanchome where there are many restaurants and shopping are and Kabukicho (biggest red light district where there are all the bars) is also only 5 minute walk distance. Even thought it is almost in the center of Shinjuku, the building is just a little bit off the big street so it was very quiet at night time.
We were very lucky that we were the very first customer at Seiji's place, sofas in the living area and other equipment was brand new. Things were very well organized with everything labeled in English.
I highly recommend Seiji's place to everyone who come to Tokyo for business and sightseeing purposes.