The Type A Mod.2 submarines were versions of the preceding A2 class with the command facilities replaced by an enlarged aircraft hangar, which was fitted for a pair of Aichi M6A1 floatplane bombers.

For surface running, the boats were powered by two 2,200-brake-horsepower (1,641 kW) diesel engines, each driving one propeller shaft.

[3] On the surface, the AMs had a range of 21,000 nautical miles (39,000 km; 24,000 mi) at 16 knots (30 km/h; 18 mph); submerged, they had a range of 60 nmi (110 km; 69 mi) at 3 knots (5.6 km/h; 3.5 mph).

It was offset to the right of, and was faired into the base of, the conning tower which protruded over the left side of the hull.

"Type AM" might also be a miss-translation of Kai Ni (改二) (equivalent to 2nd remodel/modification) being interpreted as "Mark 2" in the sense of the 1st remodel/modification.