There is actually no Presidents Club in NRT. CO has a reciprocity agreement with the JL Sakura Lounge in Terminal 2, so if you ask at the ticket counter or transfer counter, upon showing your BusinessFirst ticket CO personnel will give you an invitation paper (essentially a directional map), or you can just head over directly to the Sakura Lounge if you are a PC member.

My only actual experience doing this is as a CO Presidents Club member, not flying BF, but in my experience, unlike CO clubs, a guest is not allowed when using the JL lounge, probably because CO has to pay. Sometimes they have just let me in; occasionally they have called CO first.

Should you get over to Terminal 1 for some reason, you can probably get into the NW lounges on a BF ticket, certainly so as a PC member.

If this is your first time at NRT, there are some very helpful maps of Terminal 1 and Terminal 2 available for free in distribution racks around the airport.