Hi CJ,
If I were you I'd get in touch ASAP with HRO to ask about contracting companies. Just do a google search for something like yokosuka HRO DSN and you should be able to get a phone number. You'll want to do it sooner rather than later since the security clearance process can take forever. You'll find that, for the most part, you need to do a lot of legwork I bet. Probably calling the various commands and asking them individually what contracting company to contact and for a POC. You'll be ahead of the game since you're a spouse, because they generally get preference in GS positions, as well as being ahead of the game as a local hire since you'll not put the contracting company on the hook for relocation expenses. You might find it possible to negotiate salary if they would normally pay relocation (I think GS-9 and higher or equivalent, but I'm not really sure).
You won't need any Japanese skills in all likelihood for any DoD contracting jobs or GS positions. They might be helpful, but quite frankly the level of Japanese spoken by Americans on base is, with extremely rare exceptions, dreadfully low.