Design of a four-engine bomber with a pressurized cabin and having a radius of action of 2796 st miles with a bomb-load of 8,818 lb was undertaken by Kawasaki in May 1943. Planned production was suspended in February 1945 when tooling was destroyed during a B-29 raid before completion of the prototype. Power-operated turrets housing two 20mm cannon were to be installed, one in the nose, one above the fuselage and two mounted beneath the fuselage. A four-cannon turret was planned for the tail position. (info is from Francillion)

Kawasaki Ki-91

Type: heavy bomber
Crew: n/a
Armament: see above
Reference: Francillon: 484
Specifications:
Length: 108' 3.25" (33 m)
Height: n/a
Wingspan: 157' 5.75" (48 m)
Wing area: n/a
Empty Weight: n/a
Loaded Weight: 127,868 lbs (58,000 kg)
Max Weight: n/a
Propulsion:
No. of Engines: 4
Powerplant: Mitsubishi Ha-124 Ru radial
Horsepower: 2500 hp each
Performance:
Range: 6214 st miles (10,000 km)
Cruise Speed: n/a
Max Speed: 360 mph (580 km/h) at 32810 ft
Climb to/in: n/a
Ceiling: n/a
Production: no aircraft constructed