The 100 series trains entered service on 1 June 1990 on Kegon and Kinu services from Asakusa in Tokyo to Nikkō and Kinugawa-Onsen, replacing the ageing 1720 series trains operating since 1960. Two sets were delivered in fiscal 1989, two more were delivered in fiscal 1990, and five were delivered in fiscal 1991, bringing the fleet to nine sets.
