It depends what kind of food you like...
Teppenyaki is great, if they do that. That's when the food is cooked in front of you on a hot plate...steak, chicken, seafood, tofu...whatever you like. You can choose how you want it cooked, and it's good fun if there's a group of you as the chef normally puts on a bit of a show.
Other than that, there's sushi or sashimi. Sashimi is incredibly fresh fish, cut into portions and served raw with dipping sauces. Sounds scary, but it's absolutely delicious. Sushi is similar, but rice based. It can include raw fish, but also vegetables, and some cooked ingredients too.
Definitely try miso. It's a very delicate soup flavoured with seawood and fish stocks. Beautiful.
If in doubt, just ask the staff what things are. I'm sure you'll love it. Once you turn Japanese, there's no going back!
Enjoy!