[1][2] In late 1970s, it was clear that the new international rules on exclusive economic zone would need a considerable increase in the size of the Maritime Safety Agency fleets.

In order to cover a wide ocean with a small number of vessels, JMSA began considering the shipping operation of air-sea rescue helicopters.

[1] In particular, the overall improvement was added to the design of the last two vessels, so the United States Naval Institute dealt them as a separate group, Ryukyu class.

[6] In the Incident of Suspicious Boats off the Coast of Noto Peninsula, Chikuzen acted as a forward operating base of the Special Security Team (SST).

She also fired warning shots by her JM61-M.[7] With their high-endurance and aviation patrol capability, these ships also attend to overseas dispatch including counter-piracy operations in the Strait of Malacca.