Iyo personifies the Iyokan Railway Kō 1-1 steam locomotive, famously known as the Botchan Ressha. Her easygoing nature contrasts with a distinct aversion to insects, though she tolerates a few aesthetically pleasing ones; this aversion is complicated by insects' tendency to be drawn to her. She possesses long blonde hair extending past her midsection and vibrant blue eyes. Her attire is a distinctive green railroad uniform adorned with green and gold stripes and red accents featuring brass buttons, topped with a tan-colored hat. Her small stature reflects the compact, often toy-like appearance of her locomotive.

The Botchan Ressha she represents is a narrow-gauge steam engine built by Krauss & Co., imported to Japan in 1888. It operated on the Iyokan Railway in Ehime, Shikoku, from 1891 to 1954, running on coal along the 4.5-mile route between Matsuyama City and Mitsuhama Port. Its cultural fame stems from an appearance in Natsume Soseki's 1906 novel *Botchan*. The original locomotive rests preserved at Baishinji Garden, while replicas are displayed at the Botchan Ressha Museum and operate as tourist trains between Komachi Station and Dogo Onsen. Iyo's green uniform with red accents and brass buttons directly mirrors the locomotive's livery.