The Cruiser submarine Type-C was one of the first classes of submarine in the Imperial Japanese Navy (IJN) to serve during the Second World War. Type-C submarines were better armed than the Type-A and Type-B. The Type-Cs were also utilized as Kō-hyōteki or Kaiten mother ships, for this reason they were not equipped with aviation facilities.

The Type A Ko-hyoteki class was a class of Japanese midget submarines (Kō-hyōteki) used during World War II. They had hull numbers but no names. For simplicity, they are most often referred to by the hull number of the mother submarine. Thus, the midget carried by I-16-class submarine was known as I-16's boat, or "I-16tou."