Regarded only as an interim type, the Navy wanted a torpedo bomber offering performance comparable to the Mitsubishi A5M monoplane fighter.

The result was a biplane with fixed landing gear and an all-metal structure with metal or fabric skin.

In 1940, the Nakajima B5N replaced the B4Y1 as the primary carrier attack aircraft, though the B4Y1 did remain in service as an advanced trainer, and flew from Hōshō and Unyō until 1943.

Before its replacement, the B4Y1 had flown during the Second Sino-Japanese War and served at the Battle of Midway during June 1942, where eight of them were operated from Hōshō.

[4] The B4Y1 was operated from the aircraft carriers Akagi, Hōshō, Kaga, Ryūjō, Sōryū, and Unyō, as well as the 13th and 15th Kōkūtai (Air Groups).