The "Lily", in some respects, was a somewhat backward-looking aircraft.  Among its less advanced features were the open cockpit for the rear-firing dorsal machine-gunner and, here, the open "drop-down hatch" arrangement accommodating the ventral gunner.  Presumably, this hatch had to remain open for the duration of any flight or part of a flight in which a threat from enemy fighters existed.  I cannot say that I would have envied the gunners ... JR.

Keep hanging on - Kawasaki K-48 ventral gunner.

Developed in response to a 1937 commission for a fast light bomber, the Ki-48 served in virtually all theatres of Japan's Pacific and Chinese wars.  Even in the improved II versions, the aircraft proved vulnerable to Allied fighters in the Pacific War, but could function reasonably effectively in small formations under heavy fighter escort.  As a result, the aircraft was produced into 1944, and examples of all marks and sub-marks (including the inferior Ki-48-1s) continued in frontline service until mid-late 1944.  Increasingly effective Allied fighter opposition resulted in instances of heavy losses (some virtual massacres), which prompted the Japanese to retire the aircraft from the front line; by that stage, the Ki-48, of whatever type, was distinctly obsolete.  The aircraft was then converted to Kamikaze use; it still seems to have required considerable fighter escort to have much chance of reaching its targets.  Best regards, JR.

"Fast bomber" - Kawasaki Ki-48 "Lily".

Pilots of the Japanese Imperial Navy are ready to take off with their Yokosuka P1Y "Ginga" bomber (code name known by the Allies as "Francis"), from an airfield on the Mariana Islands.
The Yokosuka P1Y Ginga was a twin-engine, land-based bomber developed for the Japanese Imperial Navy in World War II.