North Korea began the war armed with the Shpagin PPSh41 Burp Gun as the standard personal weapon for submachine gunners. The CCF also used it, but employed a bewildering array of other automatic weapons, as well, possibly including these Japanese guns.

Until the thirties, the Japanese purchased Bergmann submachine guns manufactured by SIG in Switzerland. These are basically the MP 18.1 modified for a box magazine and chambered for the 7.63mm Mauser cartridge, with a bayonet mounting bar. The Type 100 was developed as a replacement, in 1940.

The Type 100 may be fitted with a bipod, and comes in three basic models:
With fixed stock and bayonet lug bar, possibly also with a compensator.
With folding stock and bayonet lug bar.
c1944, with fixed stock, bayonet lug on barrel jacket, compensator, and fixed aperture-type rear sight.