In sharp contrast with the introduction of commuter train series 103 on the Keihanshin Local Line, JNR took quick action to introduce new cars to the line to meet the requirements of the Katamachi Line and Kansai Line to replace, as soon as possible, their aging train series 101 and to improve their comparatively lower ratio of air-conditioned cars.
103系のときとは打って変わった素早い新車投入であったが、これには片町線、関西線の老朽101系の早期取替えと、他線に比べて低い両線の冷房化率の向上という背景があった。