The Agano class were designed in the late 1930s to replace the older 5,000 ton cruisers that were armed with 5.5" guns. The Agano class ships were to be the flagships of destroyer squadrons.
Originally the Agano class was to have three triple turrets but it was decided to make the ships lighter so they could be used as scouting cruisers and have four twin turrets. Then the X turret was replaced by torpedo tubes.
In March 1939 they were approved for construction under the 4th Naval Replenishment Program.
The two aircraft were carried on a platform behind the funnel. There was a single catapult for launching the aircraft. There was a crane mounted aft.
The torpedo mounts could rotate and fire either port or starboard.