In January 1966 Shin Meiwa was awarded a contract to develop a new anti-submarine flying-boat for the JMSDF. Company designated SS-2, the flying-boat was also adapted for amphibious operation as the SS-2A. In the ASW configuration the SS-2 received the JMSDF designation PS-1, while as a search and rescue aircraft it was designated US-1.

The first PS-1 prototype flew on 5 October 1967. By March 1979 Shin Meiwa had delivered two prototypes and 22 production PS-1s to the JMSDF, serving with the 31st Air Group for ASW duties.

The first US-1 flew on 16 October 1974. A total of 12 US-1s were built by 1988.

In cooperation with the JMSDF and the National Fire Agency, Shin Meiwa converted the first PS-1 prototype into a water-bombing test-bed; it could deliver a total of 185 tonnes of water, picked up 70km from base, to a site 10km away, in 3 hours 36 minutes. The proposed production version could deliver 315 tonnes to a site the same distance from its base before needing to refuel.