Jōban Line
In late 2014 and early 2015, two Chūō–Sōbu Line sets (B20 and B21, with six-door cars substituted by two trailer cars from B22) were transferred to the Jōban Line (and renumbered 118 and 119) for the extension of the Jōban Line services to Shinagawa Station with the opening of the Ueno–Tokyo Line. This brought the total number of Jōban Line sets to 38 (19 five-car and 19 ten-car sets), all of which were refurbished between 2015 and 2020.