[1] The 781 series electric multiple unit was designed specifically for limited express services on electrified lines in the Sapporo area of Hokkaido, to replace the 485-1500 series EMUs first introduced on Ishikari services in 1975, but which proved unreliable in the harsh winter conditions of Hokkaido.

[3] Seven full-production 6-car sets were delivered from 1980, with minor improvements including the abolishment of two opening windows on each side.

[1] A second side door was added to the KuHa 780 and SaHa 780 cars between 1991 and 1993 to reduce station dwell times.

[2] Improved "u-Seat" reserved seating accommodation (rows 1 to 7) was added to half of car 4 between March and June 2001.

A complete 4-car set, consisting of cars KuHa 780-2, SaHa 780-4, MoHa 780-4, and KuMoHa 781-2, is preserved, minus the bogies, at Kikyo Kindergarten in Hakodate, Hokkaido.