Ask the Japanese about the route or price, and other conversations that will be used during the trip. The more, the better. Take romaji.

I have also been to Japan twice. It doesn't matter if you can't speak Japanese. You can use English sometimes. If you want to go somewhere, check the address in advance and write it down. When you take a taxi, you can hand in your papers directly. If you buy something, just order it directly. If not, just draw a bill on the paper and put a question mark. That's what I did when I traveled all the way in Japan.