This helps to send a message to China about the rising will of the Japanese government to project naval power:
One of Japan’s largest warships, the helicopter carrier Izumo, offers a glimpse of where its military is headed: For the first time, troops from a newly formed amphibious brigade of the Self-Defense Forces participated in an extended naval deployment.
The Izumo left Subic, a former U.S. naval base in the Philippines, at the end of a two-month deployment in the Indo-Pacific region at a time of prolonged tensions involving China’s sweeping territorial claims in and around the South China Sea. The carrier, along with the destroyers Murasame and Akebono, just finished a series of drills with the United States and other countries.
Japan’s ability to project military power beyond its borders is severely constrained by the commitment to pacifism and rejection of use of military force in conflict enshrined in its post-World War II Constitution, though in 2015 it was reinterpreted to allow the use of force in defending itself and its allies.
Prime Minister Shinzo Abe has made amending the Constitution to allow the military greater leeway one of his lifetime goals. President Donald Trump has sought to help that cause, calling repeatedly for Japan to do more to defend itself under its alliance with the U.S.
In May, Japan conducted its first quadrilateral exercise with France, the U.S. and Australia in the Bay of Bengal. France deployed its flagship nuclear-powered aircraft carrier, the FS Charles de Gaulle, while the United States sent a missile destroyer, the William P. Lawrence. Other drills have included Canada, India, Malaysia, Vietnam, Brunei and the Philippines.
Japan is preparing to reconfigure the Izumo to accommodate U.S. stealth fighters, including F-35Bs, after announcing it would purchase 42 of its own. The aircraft are designed to operate with short takeoffs and vertical landings, such as on carriers.
Japan Times
You can read more at the link, but the Japanese carriers are going to be able to project quite a bit more power once they are equipped with the F-35B’s.