Shop: Tokyu Hands
This seven-level department store is like the love child of Paper Source, Muji, Flight 001, and the Home Depot, but is so much better than the sum of its parts. My personal wonderland was this wall of washi tape. If you make it all the way to the top floor you'll be rewarded with an adorable cafe that serves caramel ice cream with potato chips.

Also Noted: 
FOUND Muji, a small housewares shop in Aoyama curated by the stylesetting retailer.
Kiddyland, an incredible Harajuku toy store that adults will obsess over too.