[1] From 2009, some Keihin–Tōhoku–Negishi Line-allocated sets were transferred and refurbished to operate throughout the Bōsō Peninsula, following the introduction of newer E233 series trains.

Much of the Bōsō-allocated fleet was replaced from 2021 by new E131 series trains, following many of the lines within the region being modified to accommodate one-man operation.

[1] In July 2021, Izukyu Corporation announced its plan to procure 209 series trains that were previously operated by JR East on services throughout the Bōsō Peninsula.

They are also the first trains operated by Izukyu to use variable-frequency drive (VVVF) technology and also did not require large-scale refurbishment.

In contrast, the older 8000 series trains inherited from Tokyu Corporation required the installation of toilets, onboard passenger information displays, electrical coupling, and transverse seating; these features were already included with the 3000 series sets upon their inheritance by Izukyu Corporation.