Junsen 1M
Built under the 1928-1931 program. First Japanese submarine with a seaplane. Project was grounded on Junsen 1 type. Basic difference consisted in absence of 140mm gun and two watertight cylindrical containers, installed aside on an upper deck, astern from CT, in which the taken apart seaplane (in one container took places the case and floats, and in second wings) was stored. Assemblage was effected on a deck behind CT. Originally aircraft launched from water. In May, 1933 submarine was equipped with a catapult mounted on a deck astern from CT. Launch was realised against the course. Aviation armament of this submarine had in many respects experimental character. Launch of aircrafts against a course has been recognised by unsuccessful, as well as seaplane storage in the taken apart kind.
Koryu
The Koryu (Type D) was an improved version of the Type C midget. Type D's were equipped with more powerful diesels and electric motors and could recharge their batteries faster. These changes again tripled their range. They were four feet longer, weighed 60 tons and could dive to 328 feet. The the first Type D boat, HA-77, was completed in January 1945. By war's end, 115 were completed and another 496 hulls were in various stages of construction. At least five Type D's were lost in operations at Okinawa in March 1945.
Kairyu
The Kairyus were originally designed as midget submarines with torpedo tubes. Because of the lack of torpedoes, and because their mission was near-suicidal at best, most were equipped as suicide craft with a 600 kilogram charge instead of torpedoes. 760 were ordered but only 213 had been delivered by the time of the surrender, and none of these carried out a combat mission.
