On November 1, 1942 the Tainan Kokutai was redesignated the 251 Kōkūtai (251 Air Group). During May 1943 the unit received two J1N1 Gekko (Irving) night fighters armed with upward and downward firing 20mm cannons. Flying from Lakunai Airfield near Rabaul, Ono became the second Gekko pilot flying with Shigetoshi Kudo.
June 10, 1943
Ono took off with Lt. (jg) Kisaku Hamano as observer to intercept 20 bombers attacking Rabaul, this was the second time that J1N1 Gekkos were used as night fighters. Attacked a B-17 caught in search lights at 4:02am a 7,000' and attacked from 1,500' below opening fire at 4:04 and observed hits of his 20mm cannons in the left wing. The bomber lost altitude and disappeared into the darkness at 2,000' about eight minutes after the attack. At 4:48 Ono spotted a second bomber in searchlights and attacked it, 20 minutes later. He finally hit the bomber in the right wing and saw it catch fire, but the flames were extinguished and it disappeared into the night. Japanese claimed one bomber destroyed and on probable this night.
On the American side, 43rd BG lost no bombers that night, but one radio operator from 63rd BS was injured by gun fire from a night fighter.
June 13, 1943
Took off with Hamano as observer at 02:40am, followed three minutes later by J1N1 piloted by Kudo/Sugawara. Ono could find no enemy aircraft and landed at 05:40am.
Claims in J1N1
June 13, 1943 claimed 1 x B-17 and 1 probable B-17 * in fact, none lost
June 17, 1943
On June 17, 1943 a pair of J1N1 Irving night fighters of the 251 Kōkūtai took off from Ballale Airfield at 0225. One piloted by Okado with observer Satoru Ono sighted a B-24 [PB4Y 31952] flying in the opposite direction and made three strafing run against the plane at 3:47, and observed it going down in flames. Afterwards, both night fighters returned to base.
June 30, 1943
On June 30, 1943 J1N1 Irving piloted by Satoru Ono with observer Okado claim a B-24 shot down. This claim has not been linked to any specific loss. That same night, J1N1 Irving piloted by Shigetoshi Kudo shot down B-17F "Pluto" 41-24543 who also claimed a probable B-24.
Kodochosho, 251 Kōkūtai, July 17, 1943
Moonlight Interceptor (1985) pages 38-39
Naval Night Fighters by Yoji Watanabe 28 - 45
Thanks to Henry Sakaida, Osamu Tagaya and Edward Rogers for additional information