[4] The system's ability to produce a solfège scale when accelerating became emblematic of the 2100 series when it was introduced, earning it the "singing train" (歌う電車, utau densha) nickname.

Due to the unavailability of substitute parts for the train's GTO-VVVF system,[5] it was eventually replaced with a new inverter, which does not have a solfège scale.

[10] Keikyu collaborated with Sega to decorate a special limited-edition "Sonic the Hedgehog/Puyo Puyo" train, which ran on the Keikyū Airport Line from 14 November 2016 to 17 December 2016 to celebrate the 25th anniversary for both games.

The train was part of the Keikyu 2100 series' "Keikyu Blue Sky Train" livery and featured images of Sonic characters Sonic, Tails, Knuckles, Amy, Shadow, Silver, Doctor Eggman, and Carbuncle, as well as a collection of Puyo Puyo's expressive stacking blobs.

In addition, signs at the Airport Line's Ōtorii Station, the closest stop to the site of Sega's original office prior to 2018, featured special images honoring the games.