"Hiyō" had returned to Japan in December and "Jun'yō" followed in February. Both ships returned to Truk in late March and their air groups were detached from in early April to participate in Operation I-Go, a land-based aerial offensive against Allied bases in the Solomon Islands and New Guinea. The ships returned to Japan in late May and sailed for Truk on 7 June, but "Hiyō" was torpedoed that evening and forced to return to port for repairs. Her fighters were flown to Truk by 15 July and assigned to the light carrier . The ship was under repair at Yokosuka until 15 September. "Jun'yō"s air group was deployed to Buin, Papua New Guinea on 2 July in response to the American invasion of Rendova Island on 30 June. Leaving her aircraft behind, the carrier returned to Japan in late July.