Designed by Herbert Smith and other ex members of the Sopwith Company after The Great War, the Mitsubishi 1MT was a unique aircraft design. They had designed for Mitsubishi and the Imperial Japanese Navy Air Service what most navies were looking for, a single seat torpedo bomber.
While the British had the Sopwith Cuckoo and the Blackburn Dart as part of their carrier air groups the Imperial Japanese Navy Air Service and the Mitsubishi wanted one of there own. The designed 1MT was tested after the Cuckoo and contemporary with the Dart.
What the Japanese wanted was an aircraft that could take off and land on their new aircraft carrier, Hōshō. That would have been an improvement over the Cuckoo, which could not initially land on the Royal Navy carriers. What the Japanese found was an aircraft that was difficult to fly and could not take off of a carrier while carrying a torpedo. That could be a problem.
What the Japanese ended up doing is purchasing a Blackburn Dart for review. They were latter to design (with the help of Herbert Smith) the Mitsubishi B1M, an effective torpedo bomber that was built in large numbers, 443 aircraft, and was combat tested over China. The B1M also added a second crewman that was useful for reconnaissance. This was a good aircraft for the period.
While most were scraped after a short term of service, I wonder if any were around for the final defense of the Home Islands in World War II. Can you image the gun camera film of a F6F pilot shooting down a 1MT kamikaze? Probably not.
Image is from Wikipedia.