Im in Japan right now
if you have a iphone download a suica cars and connect it with a credit card. It makes traveling on the underground and trains soo much easier. If you dont have an iphone, buy a physical card when you arrive
set up google translate on your phone and download the Japanese dictionary so it will work offline..you can scan Japanese characters and it will translate it, you can also audio translate train announcements and get it to talk to taxi drivers etc
set up a Visit Japan account and pre clear the immigration and customs forms
https://www.vjw.digital.go.jp/main/#/vjwplo001
be prepared for Onsens being naked..its actually Ok
you will need some Yen, so set up a cashpoint card so you can withdraw some cash in Japan
Most people speak some English and most official signs have English, most atm /dinner ticket/train ticket machines have a English language option
Everything leaves on time, if you are 10 seconds late, you will miss it
Our hotel rooms all provided nice soap and shampoo/conditioner, so you dont really need your own
be aware of standing in the way or talking loudly in public, its not the Japanese way
have fun, its awesome here