The name was derived from the Kaigun-shiki Chū-gata Sensuikan (海軍式中型潜水艦, Navy Medium Type submarine).

Most of these submarines were destroyed in combat, suffering from Allied anti-submarine warfare measures, and only Ro-50 survived the war.

In 1910s, the Imperial Japanese Navy (IJN) bought a license of Schneider-Laubeuf design submarine.

The IJN official designation of these boats was Special Purpose-Medium Type submarine (特中型潜水艦, Toku-Chū-gata sensuikan).

They were planned as a prototype for a mass production submarines in the wartime under the Maru 1 Programme.