Did they have unique submarines?

Many Japanese submarines were unique. There were many different classes and variants within the classes.

1. As indicated above, many carried aircraft, mostly for scouting purposes. These were intended to locate the opposing fleet. After reporting the location of the enemy, the submarine was to attack and sink some of the enemy ships before the big gun battles.
2. Japan had a couple classes of transport submarines. They tried to import some raw materials, engineers and designs from Germany using submarines. They also used submarines to resupply garrisons that we had bypassed during our “island hopping” campaigns in the Pacific.
3. There were also a tanker submarine and a small class of minelaying boats.
4. Perhaps the most famous were the very large, aircraft carrying submarines that were intended to be used to attack New York and other American cities, as well as the locks in the Panama Canal. However, those attacks were never actually attempted.
5. The Japanese were given a couple German submarines. However, the Japanese did not appear to try to duplicate these boats. Instead, they used the U-boats as trainers.
6. There were midget submarines of about 50 to 60 tons and a crew of just two. Five of these small submarines were used during the attack on Pearl Harbor.
7. Late in the war, there were also the Kaiten submarines. These were very small submarines of less than 20 tons with usually only one man aboard. These are often thought of as the suicide submarines. The design of the Kaiten was essentially a variant of the Type 93 torpedo with a section added for the pilot.