The line uses a fleet of LE-Car II series diesel railcars classified "Isumi Class 200".

Built by Niigata Transys, this car is based on the Isumi Class 300 design, but has longitudinal seating and no toilet.

Designed to resemble the former JNR KiHa 20 DMU, the car is finished in the standard Isumi Railway livery of yellow with green bodyside stipes.

However, the route already had an existing 609 mm (2 ft) gauge human-powered tramway, which had been opened by the Chiba Prefectural government on 15 December 1912 to connect Ōhara and Ōtaki.

The tramway was bought out by the Japanese Government Railways in 1927, and the first section of the new Kihara Line (木原線) was opened on 1 April 1930.

The line problems were compounded in the summer of 1970, when heavy rains washed out a portion of the track, causing a suspension of operations from 1 July through 1 October.