Will , or could Japan take action on their own , in a millitary sense ? After all it is their territorial space that was violated.Are they handicapped by America ?
Japan is hampered by article 9 of their constitution which was adopted after WW2.
ARTICLE 9. (1) Aspiring sincerely to an international peace based on justice and order, the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes.
(2) In order to accomplish the aim of the preceding paragraph, land, sea, and air forces, as well as other war potential, will never be maintained. The right of belligerency of the state will not be recognized.
They do have some military force which they will use for defensive purposes. They are discussing revising article 9 but its a divisive issue.