The Kansai Coal Mining Co. opened a 12 km (7.5 mi), 2 ft 6 in (762 mm) gauge line from Saza to Sechibaru via Yoshii in 1896.

The then isolated Hidariishi - Ainoura section was opened as a 2 ft 6 in (762 mm) gauge line by the Sasebo Light Railway (佐世保軽便鉄道, Sasebo Keibin Tetsudō) for coal transportation on 27 March 1920,[1] and extended to Kami-Sasebo the following year.

In 1931, it was extended to Saza, with the company acquiring the Kansai Coal line to Sechibaru in 1933 and passenger services to Yoshii commencing in 1934.

[1] Between 1943 and 1944, the line was regauged to 1,067 mm (3 ft 6 in),[1] with a new alignment opened in March 1945, linking the two sections.

[1] From 1 April 1988, the line between Arita and Sasebo was transferred from JNR operation to the privately owned Matsuura Railway.