On February 27, 1942, while forming part of ABDA's Western Striking Force, HMAS Hobart was bombed by 8 Japanese aircraft while returning to Tandjoeng Priok from an abortive sortie into the Western Java Sea. Per several records, the WSF put into port at 1420 JST after having been bombed; Hobart was near-missed and lightly damaged with 5 crew wounded.
G. Herman Gill in The Australian Navy At War, Volume 2 (page 608) simply says "8 aircraft" without ID of their unit.
Bloody Shamble, Volume 2 (Page 233) says that Betty bombers of the Kanoya Ku and Nell bombers of the Mihoro Ku were operating over the western Java Sea at the time. Also Betty bombers from Takao Ku. But according to this source, none made an attack.
In his "Chronology of the War at Sea, 1939-45" (Page 126) Rowher says "A sortie made by the Allied Western Force with the cruisers Danae, Dragon and Hobart and the destroyers Scout and Tenedos from Batavia to the area of Banka and Billiton on 26-27 February finds nothing. However, attacks by Japanese aircraft from Ryujo, Chiyoda and Kamikawa Maru are also unsuccessful."
It would seem like Ryujo, Chiyoda and Kamikawa Maru are the most likely culprits. Does anyone have more info on this attack or attacks?
CHIYODA is definitely wrong. RYUJO maybe (I know where her kodochosho are, but much too busy at present to do that research. Her planes are involved in the bombings of Feb. 15th in the Gaspar Strait mess.)
KAMIKAWA MARU maybe...Can't tell from her combinedfleet TROM.
However, Howden's WesStrikFor was being shadowed and tracked, with accurate reports, all the time by Sentai 7 planes, among others.
Wouldn't surprise me if some 11th Koku Kantai planes were involved, though.