The Ha-201's were designed from the outset to have high underwater speed and were based on the earlier Submarine No.71 prototype.

[1] At the end of 1944, the Imperial Japanese Navy decided it needed large numbers of high-speed coastal submarines to defend the Japanese Home Islands[2] against an anticipated Allied invasion (named Operation Downfall by the Allies).

[2] For surface running, the submarines were powered by a single 400-brake-horsepower (298 kW) diesel engine that drove one propeller shaft.

[2] On the surface, the Ha-201-class submarines had a range of 3,000 nautical miles (5,600 km; 3,500 mi) at 10 knots (19 km/h; 12 mph); submerged, they had a range of 105 nmi (194 km; 121 mi) at 2 knots (3.7 km/h; 2.3 mph).

4911 through 4989) under the Maru Sen Programme, prefabricating large sections of the boats, then completing them on the slipway.