IIRC the Japanese constitution does not allow for offensive forces. I believe that was an agreement coming out of WW2.
1 second search:
en.wikipedia.org
Under
Article 9 of the
1947 constitution, which was written by Prime Minister
Kijūrō Shidehara under the supervision of the
SCAP,
[17] Japan forever renounces war as an instrument for settling international disputes and declared that Japan will never again maintain "land, sea, or air forces or another war potential."
[1] Later cabinets interpreted these provisions as not denying the nation the inherent right to self-defense and, with the encouragement of the United States, developed the JSDF step by step.
On 1 July 1954, the National Security Board was reorganized as the Defense Agency, and the National Security Force was reorganized afterwards as the
Japan Ground Self-Defense Force (
de facto post-war Japanese
Army), the Coastal Safety Force was reorganized as the
Japan Maritime Self-Defense Force (
de facto post-war Japanese
Navy),
[14][15] and the
Japan Air Self-Defense Force (
de facto post-war Japanese
Air Force) was established as a new branch of JSDF. General
Keizō Hayashi was appointed the first Chairman of Joint Staff Council—professional head of the three branches. The enabling legislation for this was the 1954
Self-Defense Forces Act [
ja] (Act No. 165 of 1954).