The Type KiHa-Yuni 15 of the Japanese National Railways was created between 1957 and 1958 by rebuilding the Type KiHa 44000 (later redesignated as the first-generation KiHa 09 class), which had originally been introduced in 1952 as electric-transmission diesel railcars with a “Shōnan-style” front design.
During this rebuilding program, the vehicles were converted to the more common hydraulic-transmission diesel configuration.
In addition, some cars were later modified with gangway-equipped (through-type) front ends.