Since this would entail enormous costs and years of work, it was decided to further increase the transportation capacity of the narrow-gauge line.

To allow for the use of low-quality lignite with a calorific value of 4,500 kcal (19,000 kJ), the firegrate area was made 2.1 m2 (23 sq ft) - a size comparable to that of the Japanese Government Railways' Class 9600 engines;[2] naturally, this made the firebox wider than on other narrow-gauge locomotives.

To ensure that this would allow the locomotive to clear a curve of such small diameter, at the suggestion of Kisha Seizō chairman Yasujirō Shima,[3] a full-size wooden mockup of the locomotive was built and tested on a curved track.

Locomotives of this design were later built by Nippon Sharyō for the Taiwan Railway Bureau for use on the Taitung Line.

The three Hitachi-built units are known to have operated with the KNR, which designated them 혀기11 (Hokey11) class and numbered 혀기11-12(Hokey11-12), 혀기11-13(Hokey11-13) and 혀기11-14(Hokey11-14); all three are preserved.