The C12 was a class of 2-6-2T “Prairie” tank locomotives built for mixed traffic on branch lines with a low axle load limit. It was designed by Hideo Shima in the early thirties, together with the C56 2-6-0. This meant that the cylinder and driver dimensions were identical and the boilers were very similar. From C12 38, all locomotives had arch tubes in the firebox which increased the direct heating surface from 7.4 to 8.3 square metres. After production had been stopped in 1943, Nippon Sharyō built the last 18 in 1947 and there were even 42 more incomplete locomotives. In total, 282 were completed. In Japan, the last ones were withdrawn in 1975. At least 26 are surviving, of which C12 66 is the last one that is still in running condition.

In 1938 and 1939, 60 were rebuilt to metre gauge for the North China Transportation Company and called “PureA”. Later China Railway designated them PL51. When the line where they were operated was converted to standard gauge, all came to Vietnam in 1956 and became class 131. One is being preserved and another one was allegedly still operated by a private operator between a mine and a steel works in 2002. Seven locomotives were built new for the Taiwan Railways and became class CK120. In 1943, the Japanese Army decided to send two to Indonesia. There they were designated class C32 and were used as shunters until the eighties.