Grant M.
Google
Like others here, I was confused about the exact location of this store. It's inside the JR train gates, not the subway. The train has a Marunouchi central underground and a south underground exit. It's between the two, right by some escalators. I think the pin is in the right place, just remember it's inside the JR train's underground gates. They have a lot of selection for a small store, and a steady stream of customers, but it wasn't crowded. Definitely worth it if you're a train fan.