heads of the three branches of government
Refers collectively to the leaders of Japan's legislative, executive, and judicial branches: the Speaker of the House of Representatives, the Prime Minister, and the Chief Justice of the Supreme Court. Used in political and legal contexts.
It is rare for the heads of the three branches of government to gather in one place.
Compound of 三権 (three powers, i.e., legislative, executive, judicial) + の (possessive particle) + 長 (head, leader).