In 1928 Mitsubishi hired Herbert Smith, formerly with Sopwith Aviation, to design a trainer that could carry three or four pupils. He submitted a design for an all wood biplane in December 1928 and it was initially designated the M-13. However no prototype was constructed as the military showed no interest.
In 1929 the Imperial Japanese Navy asked Mitsubishi to develop a crew trainer. Two prototypes of the Ka-2, designed by Hattori, were ordered. It had a metal fuselage and a high wing parasol. It was initially designated the 4MS1.
By 1933 the Army also became interested and a modified version was designed by Masakishi Mizumo. It initially was designated the Ki-7.
The Mitsubishi K3M was a popular crew trainer.