Based on the Nankai 12000 series EMU design introduced in 2011 on Nankai Main Line Southern services, the Semboku 12000 series sports a gold livery and has different coloured seat covers in each of the four cars.

[1] The 12000 series is a four-car trainset, accommodating a total of 242 seated passengers.

[4] The four-car trainset, 12021, was delivered from the J-TREC factory in Yokohama to Wakayamashi in October 2016.

[5] On 21 January 2017, set 12021 was used on an invitation-only preview run between Kōmyōike and Namba.

[6] The trainset entered revenue service on 27 January 2017, following an official send-off ceremony at Izumi-Chūō Station.