United States Fleet Activities Yokosuka (, Yokosuka kaigunshisetsu) or Commander Fleet Activities Yokosuka (, Shirei-kan kantai katsudo Yokosuka) is a United States Navy base in Yokosuka, Japan. Its mission is to maintain and operate base facilities for the logistic, recreational, administrative support and service of the U.S. Naval Forces Japan, Seventh Fleet and other operating forces assigned in the Western Pacific. CFAY is the largest strategically important U.S. naval installation in the western Pacific. As of August 2013, it was commanded by Captain David Glenister.

Is it true that is there a us naval base in japan?
yes