1) Important documents – passport, visa if required, address of your initial accommodation, plane tickets, copy of your travel insurance etc.
2) Money – About 20,000 yen in cash. Enough to get you from the airport to your accommodation without needing to find an ATM.
3) A spare pair of eye glasses/contacts if needed.
4) Enough prescription drugs (if needed) for the length of your stay. (You will need to check in advance to make sure you can bring them into Japan – DO NOT ASSUME! – and that you have proper documentation, i.e. a note from your doctor)
5) A backpack or briefcase (for day trips & daily use). Use this as your carry-on so that you will have less luggage.
6) A gift or gifts for your host family/others. (Try to get something that is specific to the region where you live, and that is edible. Storing gifts in Tokyo can be difficult due to space, so food items are good gifts)
7) Laptop computer or tablet, with a charger.
8) Camera and charger.
9) If needed, a plug adapter and converter. Japan uses a 2 prong plug and 100 volts.
10) Hat, sunscreen, and if you have sensitive eyes, sunglasses.
11) Light, cotton clothing for the Tokyo Summer Program, warm windproof clothing if studying in winter (or Climbing Mount Fuji in summer).
12) Good walking shoes or hiking boots.
13) A pair of flip flops or sandals.
14) Key ring
15) Dictionary or suitable app.
(Suggestions always welcome!)