The Status of Forces Agreement governing U.S. Forces Japan, among other arrangements, requires this country to bow to Washington in a number of areas.
And while Tokyo and Naha continue to square off over the bases issue in Okinawa Prefecture, I would argue that both the mainland and the southernmost prefecture share the same humiliation in times of crisis due to the U.S. military presence.
They can renegotiate JOA. They can cancel the JOA and give up the trillion dollar military subsidy any time they like.