Two photos from a vintage publication of the little known Hiro G2H1.
Only eight aircraft of this type were ever produced, six by Hiro and two by Mitsubishi.
Although not exactly known which went where, six of them were operated by the Kisarazu kokutai and two by the Yokosuka kokutai.
The participated in the opening stages of the Second Sino-Japanese War from an airfield on South Korea's Jeju island and belonged to the 1st Combined Kokutai starting with an air raid against the areas of Jiangwan and Nanxiang districts of Shanghai on September 30, 1937. They dropped twenty no25 (250kg) bombs and forty no6 (60kg) bombs.
On October 24, 1937 while preparing for take-off fire started on one of them from the break system and jumped to the fuel resulting in an explosion. It seems that they were very close to each other so the fire spread to other G2Hs. The remaining aircraft were joined by the other two G2H1 of the Yokosuka kokutai and all together arrived to Shanghai on November 2, 1937 where they continued their operations.
Sources do not agree. Encyclopedia vol. 3 (Nihon Kokuki Sosyu, 1963) and Mikesh&Abe mention that on the way to their deployment to Jeju island "and for unexplained reasons, one G2H dropped out of formation and crashed near the coast of Sagami Bay southwest of Tokyo". This means that there were only five aircraft left and when the 10/24 accident occurred, four were burned and one was destroyed by an explosion. That would mean that no G2H were left and do not mention the two from Yokosuka ku joining that fight.
Other sources, ex. "All the Regular Formed Aircraft in Japanese Navy" (Nihon Kaigun Seishikiki Taikan), do not mention the one which dropped out of formation but instead explain that 4 a/c were burned in the 10/24 accident and one was destroyed by an explosion, leaving only one to be joined by the two of the Yokosuka Ku. In total three aircraft arrived in Shanghai on 11/2.