Yes, if you can gain access to the NRT RCC then you can use the shower facilities. It sounds as though you have been able to gain entry to the NRT RCC, but then encountered some sort of problem when you went to use the shower? Can you share your experiences?

Regarding access to an RCC as a Star Gold I found this in another post:

S*RCC/ADMIT UPDATED 03MAY2004

* * * UNITED RED CARPET CLUB ACCESS GUIDELINES * * *
FOR US AIRWAYS NEWS >S*R.U

* * RED CARPET CLUB MEMBER ACCESS * *
A VALID RED CARPET CLUB MEMBERSHIP IS REQUIRED
GUEST POLICY:
WITHIN US: TWO GUESTS OR SPOUSE AND DEPENDENT CHILDREN
OUTSIDE US: ONE OR SPOUSE AND DEPENDENT CHILDREN
MEMBER MUST ACCOMPANY GUEST(S) AT ALL TIMES
FOR CURRENT MEMBERSHIP STATUS... CHECK MPM
MEMBERS TRAVELLING WITHOUT THEIR MEMBERSHIP CARD
MAY BE ASKED TO STEP ASIDE SHOULD THERE BE A LINE
AT THE CLUB ACCESS POINT AND SHOULD BE ASKED TO WAIT
UNTIL THE LINE CLEARS

* * * UA AND STAR INTERNATIONAL TRAVELERS * * *
UNITED FIRST INTERNATIONAL AT ALL CLUBS ON SAME-DAY
TRAVEL... ONE GUEST ALLOWED... TWO DRINK CHITS SHOULD
BE PROVIDED AT THE GATEWAY.
UNITED BUSINESS INTERNATIONAL AT ALL CLUBS ON SAME-DAY
TRAVEL... NO GUESTS ALLOWED... TWO DRINK CHITS SHOULD
BE PROVIDED AT GATEWAY.
* * * INTERNATIONAL DEFINITION * * *
TO OR FROM THE UNITED STATES EXCLUDING SAN JUAN
CUSTOMERS WHO TRAVEL TO CANADA MEXICO ARUBA AND
ST THOMAS WILL BE TREATED AS INTERNATIONAL AND
CUSTOMERS WILL HAVE ACCESS TO THE RED CARPET CLUB
THIS APPLIES TO UA CUSTOMERS(F XF NF C XC NC)
AND STAR GOLD CUSTOMERS ONLY ..SAME DAY TRAVEL IS
REQUIRED AND THIS INCLUDES CONNECTING STATIONS
ON SAME DAY TRAVEL AS LONG AS THEY ARE IN F OR C
CLASS FOR THE ENTIRE ITINERARY......
FOR EXAMPLE: LAX Y ORD F YYZ...ACCESS IN ORD ONLY
FOR EXAMPLE: LAX F ORD F YYZ ...ACCESS IN LAX AND ORD

* * STAR GOLD ACCESS - OA STAR ALLIANCE CUSTOMERS * *
STAR GOLD CUSTOMERS (EXCEPT UA AND US AIR STAR GOLD)
TRAVELING ON A SAME DAY STAR OPERATED FLIGHT
HAVE ACCESS TO RED CARPET CLUB ON DAY OF TRAVEL
CUSTOMER SHOULD PRESENT STAR GOLD CARD
AND BOARDING PASS FOR STAR OPERATED FLIGHT
* * SEE NOTE BELOW FOR UA AND US * *
** NOTE UA AND US STAR GOLD CUSTOMERS HAVE ACCESS
ONLY IN CONJUCTION WITH INTERNATIONAL TRAVEL* * *
GUESTS MUST ENTER THE LOUNGE WITH AN ELIGIBLE
STAR ALLIANCE GOLD MEMBER AND MUST DEPART ON A
STAR ALLIANCE MEMBER AIRLINE BUT MAY TRAVEL ON A
DIFFERENT FLIGHT.
TWO DRINK CHITS SHOULD BE PROVIDED AT GATEWAY.
ALL CARD HOLDERS AND GUESTS SHOULD BE TRACKED
-STAR ALLIANCE ACCESS SEE: >S*RCC/ALLIANCE
-US AIRWAYS RECIPROCAL AGREEMENT SEE: >S*RCC/US_AIRWAYS