In 1942 the Imperial Japanese Navy released the 17-Shi specification for a reconnaissance aircraft with the following specifications:
- 414 mph / 360 knots at 19,685' / 6,000 m
- Long range
- Land based
The Dai-Ichi Kaigun Koku Gijitsusho was tasked with coming up with a design. It was to use a Mitsubishi 24 cylinder (2,500 HP) liquid cooled engine then under development. As the delivery was expected much later than initially planned for two Mitsubishi MK10A radials were used. This design, the R1Y1 Seiun (blue cloud), didn't meet the specifications of the 17-Shi and was abandoned.
Then the Imperial Japanese Navy released an 18-Shi specification in early 1943. This lead to a design that was inspired by an Heinkel He 119V4 that was purchased by the Navy in 1940 by Commander Hideo Tsukada. The design had two engines behind the cockpit that would drive a single propeller. This was to become the R2Y1 Keiun (beautiful cloud).
In 1944, with the worsening war situation the Navy decided to transform the R2Y1 into a jet attack bomber. A Ne-330 turbojet was intended to be placed under each wing. This became the R2Y2.