The book "The Japanese Submarine Force and World War II" by Carl Boyd and Akihiko Yoshida describes the use of these aircraft in their Giant I-400 class submarine. Also stated that they were converted from "Judy" dive bombers. The I-400's hanger could hold three seaplanes.

This aircraft had a very complicated system of folding wings and tailplane. The wings unlocked, pivoted vertically and were folded back against the fuselage. The ailerons on the rear tailplane folded downwards towards the ground. When folded the body and wings were all contained within the diameter of the propellor.
On take off, from the submarine, the pilots were subjected to tremendous forces from the launch device.