The Oyodo was to be an improved Agano class cruiser. It was ordered under the 1939 Program / 1939 4th Replenishment Program.
The Oyodo was intended to be used as a flagship of destroyer and submarine units. However, by the time Oyodo was completed Japanese submarines were primarily being used to resuppy isolated island bases.
In place of the aft turrets there was a hanger that could hold six E15K1 "Norm" aircraft. These were to be a new model of aircraft that wasn't built so instead only two floatplanes were carried.
When the Mogami class cruisers were upgraded to 8" gun, their former 6.1" turrets were used on the Oyodo.