During WW2 the IJN used many submarines types, some conventional and some unique in concept, like the very big Sen Toku type I-400.
The small submarine RO-35 of the Kaichu-6 type
The transport submarine of the Tei Gata type, was armed only with a deck gun and her "cargo" of around 110 soldiers was transported ashore by two Daihatsu landing craft. Later some of the class mates were converted to carry 6 Kaiten suicide submarines on deck
One of the more unique submarines were the Sen Ho type, which were designed to refuell the Kawanishi H6K flying boats, and re-arm them, in areas where surface ships couldn't operate. 365t of aviation fuel and 12t of bombs and torpedoes were carried for the flying boats, as well as 11t of drinking water. Only one submarine was completed.
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Thank you Kim for the crest
"Never fear to try on something new. Remember that the Titanic was built by professionals, and the Ark by an amateur"