Ha-101-class submarine

The Ha-101 class submarine (波百一型潜水艦) was a transport submarine of the Imperial Japanese Navy (IJN), serving during late World War II. The IJN planned to build 12 boats, but only 10 vessels were completed by the end of the war. The IJN called these submarines Sen'yu-Kogata (潜輸小型). Several boats were converted to tankers or mother ships for the Kō-hyōteki model D "Kōryū" (甲標的丁型 蛟龍) midget submarines.

Planned construction
Project number S57. In February 1944, the IJN planned a small-size transport submarine, the IJA planned the Maru Yu.