At the beginning of the operation, it merely consisted of ordinary cars so a first-class car wasn't connected with it, but half of its front car was converted into a first-class section ("Kuroha 481") right after that, and the conversion of the entire rolling stock was completed until the division and privatization of JNR.
運転開始当初は普通車のみの編成で、グリーン車は連結されていなかったが、直後に先頭車を半室グリーン車（クロハ481）に改造しており、国鉄分割民営化までに全編成の改造を完了した。