The Type B submarines were derived from the earlier KD6 sub-class of the Kaidai class and were equipped with an aircraft to enhance their scouting ability.

[1] For surface running, the boats were powered by two 6,200-brake-horsepower (4,623 kW) diesel engines, each driving one propeller shaft.

[3] In the Type Bs, the aircraft hangar was faired into the base of the conning tower.

Late in the war, some of the submarines had their aircraft hangar removed, to replace it with an additional 14 cm gun.

All B1 type submarines were lost during the conflict, except for I-36, which was scuttled off Gotō Islands by the US Navy on 1 April 1946.