ANA (NH) has its lounges at Terminal 2 of NRT. If my memory serves right (I was there just a few days ago), there are three signet lounges in the main terminal section of T2 and there is another at the satellite section where you get there by a short train ride.

At the main terminal section, two are on the same floor as the passport control. One of these two, nearest to the passport control counters, doubles as Fuji Lounge and it did not have any Star Gold sign.

The third one is upstairs. (To take the train, you go downstairs.)

ANA allows a Star Gold member to check in at their F counter. I think they will issue you an invitation to whichever lounge they want you to go to. They seem to want to control the traffic in each lounge.

I visited two of the three signet in the main terminal section. The Fuji lounge was quieter but a bit smaller. The other on the same floor has two sections -- to the left and to the right. I was on an economy award ticket and flashed my NH*G card and they asked me to go to the right, where LH customers were also invited.

But at NRT, by all means, the UA lounge (at Terminal 1) is the best. Terminal 1 also has an SQ lounge. I had an SQ flight last week but did not bother going to their proprietary lounge. I went to the UA lounge. (They somehow asked me to show any UA card I had, though, which should not have been necessary.)