Propelled by a Ishikawajima Tsu-11 "motor jet". Also known as, "Campini" motor jet after the Italian Secondo Campini.
The Tsu-11 consist of an inverted inline engine which drives a compressor. Fuel is injected into air flow creating thrust similar to an after burner. The engine is a 110 hp air-cooled four-cylinder Hitachi Hatsukaze Ha 11 which is basically a license-built Hirth HM 504.
More information and photos on the Tsu-11 can be found on the Aircraft Engine Historical Society webpage on the Tsu-11
This source states...
Engineering analysis of the engine during the restoration process suggested that the fuel injection and combustion probably contributed little to the power of the engine, with most of the thrust being produced by the compressor
NASM, Jan 2014
Information from NASM
Near the end of World War II, Vice Admiral Onishi Takijiro recommended that the Japanese navy form special groups of men and aircraft to attack the American warships gathering to conduct amphibious landings in the Philippines. The Japanese used the word Tokko-tai (Special Attack) to describe these units. To the Allies, they became known as the kamikaze. By war's end, some 5,000 pilots died making Tokko attacks. The Ohka (Cherry Blossom) Model 22 was designed to allow a pilot with minimal training to drop from a Japanese navy bomber and guide his aircraft with its warhead at high speed into an Allied warship. Plans were afoot in 1944 to adapt a version of the Yokosuka P1Y Ginga (Milky Way, Allied codename FRANCIS, see NASM collection) to carry the Model 22. While several rocket-powered Ohka 11s still exist, this Ohka 22 is the only surviving version powered by a motor-jet, which consisted of a reciprocating engine that pressurized a combustion chamber into which fuel was injected and ignited. Allied forces recovered the Ohka 22 in Japan in 1945. Unlike the Ohka 11, the Ohka 22 never became operational.