So I went to the place today. I found the exactly same building you can see from the photos posted by Switch. You can't see anything from the outside, and there are no signs of "YS NET" at all. I really can't say if someone is really working there or if it is just used as a postal address for the studio. I wasn't expecting anything special at all so.. :???:
Anyway these are some pics I took today of the area, from Ebisu station to the hypotetical YS NET studio. Enjoy! 8)
http://postimg.org/image/nssrvvddr/
http://postimg.org/image/wqetrrasx/
http://postimg.org/image/s3w761cwp/
http://postimg.org/image/yqku9g3xf/
http://postimg.org/image/vrc1t8wfb/
http://postimg.org/image/ikwo0lo11/