Tonkatsu derived from a dish made with beef, called katsuretsu (cutlet). It is said that a restaurant from Ginza, in 1890, was the first to serve a dish similar to today's tonkatsu, made from pork.
Since then, tonkatsu diversified a lot and became a Japanese traditional food. I tried a lot of versions, but my favorite is one of the simplest: tonkatsu from pork fillet, served with rice, shredded cabbage, miso soup and tsukemono (Japanese pickles).
EXIF info:
Nikon D90
Lens: VR 18-55mm F/3.5-5.6G
Focal Length: 18mm
Aperture: F/3.5
Shutter Speed: 1/50s
ISO Sensitivity: ISO 400