They have the will and the power. We made them put in an article to their constitution to renounce force with the understanding that we would protect them. In a months time they could mobilize a well equipped land army and produce nuclear weaponry. In a years time they could field additional naval forces to add to the already powerful JMSDF. Once they do that they will have no use for us and we would lose several key bases.
We'd keep our bases.
However, it's time for Japan to step up and be all they can be.
If ANY nation in the world has had a free ride, it's Japan.
The should quadruple their defense budget and stand tall.
The only thing we forced into their constitution is non-aggression and nukes.
I say we give 'em a bye.