Here are always little things you should have on yourself when you travel, whether it is across the state or in another country. These are some things I have carried in Japan (both times I have been there) and recommend to have on hand before you leave your hotel.
Battery charger and cable – Having a reliable battery back-up and the right connecting cable are super important to have. I have had to recharge my phone and pocket WIFI while exploring Japan, requiring two different cables. Make sure you have a good back-up and the right cables or you might be out of luck if you don’t pay attention to that little battery sign.
RFID wallet or passport holder – I feel these are standard issue at this stage, but having a good wallet or passport holder that is RFID blocking is a must have while exploring. While Japan is safe and this kind of thing usually doesn’t happen, never say never. All it takes is one incident and you could be without your credit cards or worse, so be prepared and get some upgraded travel gear before you leave for the airport.
Pocket dictionary – Electronics can fail but a good old paper dictionary never loses its battery power. Having one on you at all times, in that backpack, can be a life-saver if you are lost for words and are looking for some help. I always make sure to pack one with me before heading out, just in case!
Reusable water bottle – Trying to be green is always a good idea and being able to refill your water bottle is a nice thing to have while traveling. Even if the refill stations are limited while traveling, you can fill up your bottle in your hotel with some bottled water before heading out for the day and avoid having to stop to buy multiple bottles or having to carry around multiple bottles while on the move.
First aid kit – Having a first aid kit is always important when you are traveling, you never know when you will need it. From a bug bite to a blister, just having a band-aid or some kind of medicine for a minor injury, having a kit is a good thing to have, plus they are cheap and easy to put together. I would recommend however to either get a basic kit and add to it or build your own. Make sure the kit you have is equipped for the place you are going. If you are heading somewhere tropical, some more bug screen and sun tan lotion would be smart to have.