This branch of Starbucks is located at the busy Shinjuku intersection on the first floor. Get in there and grab a window seat and sit and watch Tokyo go by outside.
1st Floor
Shinjyuku Green Tower Bldg., 6-14-1, Nishi-shinjyuku Shinjuku-ku TOKYO
Shinjuku Station
Good tip- but it's in Shibuya, not Shinjuku. Go to Shibuya Station, Hachikoi Exit and you'll see it.
Thanks Gaz, yes that should be Shinjuku. Check out the view on the link below