[1] The Mitsubishi model designation for this engine was A10 while it was an experimental project, in service it was known as the MK4, and known as the Ha101 & Ha111 by the Army and Kasei by the Navy.

Although originally ordered by the Imperial Japanese Navy, the Kasei was based on the earlier Mitsubishi Shinten engine, itself based originally on the Mitsubishi Kinsei.

Produced in a wide variety of models, the Kasei began with a rated power of 1,530 horsepower (1,140 kW), with a gradual evolution to 1,850 horsepower (1,380 kW) in later wartime versions.

Three variants were developed for the Japanese Navy starting in 1939.

It was also later adopted by the Imperial Japanese Army as the Ha-101 engine.