"Agano", named for the Agano River, was laid down at Sasebo Naval Arsenal on 18 June 1940, launched on 22 October 1941 and completed on 31 October 1942. She was assigned as flagship of Destroyer Squadron 10 () of the Third Fleet on 20 November after working up. The ship departed Kure six days later and arrived at Truk in the Caroline Islands on 1 December where Rear Admiral Susumu Kimura hoisted his flag aboard her the following day. On 16 December "Agano" escorted the aircraft carrier and a troop convoy to Wewak and Madang in New Guinea. The ships briefly covered the landing of Japanese forces at Hollandia before returning to Truk on 20 December.