Nakajima Ki49 "Helen"

The Nakajima Ki-49 Donryū ("Storm Dragon"), code-named "Helen" by the Allies, was a Japanese Imperial Army heavy bomber used extensively throughout the Pacific Theatre from 1941 to 1945. It saw service primarily in China, Manchuria, the Philippines, and New Guinea. It was also deployed in the 1942 bombing of Darwin, Australia, and used in late-war kamikaze attacks. 
 
Key Operational Details:
Initial Service (1941–1942): Operated in China and during the early stages of the Pacific War in the South Pacific.
Major Theatres: Heavily involved in New Guinea and the defense of the Philippines (1944).
Roles: While designed as a heavy bomber, it functioned as a maritime patrol, anti-submarine warfare (ASW) aircraft, night fighter, and trainer/transport due to its vulnerability to Allied fighters.
Kamikaze Attacks: In late 1944, surviving "Helens" were used as kamikaze aircraft against the Allied fleet during the Mindoro landing.
Units: Primary units included the 7th, 61st, 62nd, 74th, and 95th Sentai (Air Regiments). 
 
Though intended to replace the Mitsubishi Ki-21 "Sally," the Ki-49's underwhelming performance led to it being utilized for varied, sometimes desperate, roles rather than solely as a bomber.