Katsu Sando originated in 1935 at Isen, a restaurant in Ueno, Tokyo that specialized in pork cutlets. Geishas of that time enjoyed eating the tonkatsu at Isen, and a clever way to serve the cutlets was developed - by putting them between two small slices of bread so that the geishas could eat them without ruining their lipstick. The sandwich soon became a popular item, known as "the best pork cutlet sandwich", and it spread throughout the country. It remains a beloved dish to this day.