Shopping should support the route
Japan is easy to shop in, but a first trip loses pace if shopping becomes scattered stops across the map.
Plan by area
Group shopping by neighborhood: Shibuya and Omotesando for fashion and design, Ginza and Tokyo Station for polished purchases, Ueno and Kappabashi for kitchen and everyday finds.
Luggage is the real budget
Decide before the route is locked whether shopping will be a major theme. It affects luggage forwarding, hotel choice and when to buy bulky items.
What is worth the time
Prioritize things hard to find at home, strong value, better selection or meaningful everyday Japanese design. Do not let tax-free savings control the day.