Itoya is Disneyland for people who love office supplies. I have never found such a store in the US. Itoya is similar to Staples in the same way a Tesla is similar to a garbage truck.

Itoya is amazing, it's like a wonderland of stationery!

I also highly recommend kakimori, which builds custom notebooks that you can select all the parts for (binding, paper, cover, etc.). Really memorable experience, and it's in a quieter residential part of the city (but still fairly convenient/central) that feels very different from the usual tourist spots.

This was 8 floors of heaven last year. Loved it