If you are not aware, you will go through a short customs transit inspection in NRT.

Follow the signs and the crowd. There is a Sky Priority lane but you may find that regular lines are shorter and quicker.

Once you have done this you can re-enter the terminal.

If you have time and choose to visit one of the Sky Clubs and you drink beer, make sure you seek out the beer machines. Just lurk by the refreshments and you will see how it's done if you have any concerns about these marvels of modern life.