History and development
In 1935 the Imperial Japanese Navy decided to replace the earlier 40 mm Vickers "pom-pom" guns with a 25 mm Hotchkiss design. A party of Japanese officers and engineers traveled to France to evaluate the design in 1935, and an order was placed for a number of guns and mounts for evaluation. Firing tests of these guns were conducted at Yokosuka Naval Arsenal in 1935. The first few weapons were built in France under the designation “Type 94” and “Type 95”, with the mass production model produced at the Yokosuka Arsenal being designated “Type 96”.

The Japanese made a number of minor changes to the original Hotchkiss design and production process, changing some components from forgings to castings to simplify production, and replacing the simple conical flash suppressor with a Rheinmetall-type design. A submarine-mountable version of the gun which made extensive use of stainless steel was also produced.

The double-mount type was the first to enter service, with triple mounts following in 1941 and finally single mounts later in 1943.