An Unadon is a popular donburi

Donburi

Donburi is a Japanese "rice bowl dish" consisting of fish, meat, vegetables or other ingredients simmered together and served over rice. Donburi meals are served in oversized rice bowls also called donburi...

 (rice bowl) dish made with unagi

Unagi

Unagi is the Japanese word for freshwater eels, especially the Japanese eel, Anguilla japonica. Saltwater eels are known as anago in Japanese. Unagi are a common ingredient in Japanese cooking...

kabayaki

Kabayaki

is a generic Japanese term for a dish of seafood which is filleted, boned and dipped in a sweet soy sauce-base sauce before broiled on a grill. In general, kabayaki refers to the dish made with unagi. Kabayaki eel is very popular as a nutritious, stamina-generating food...

, grilled eel

Eel

Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...

 coated with a sweet sauce.

Variations include unajū (鰻重, the same dish served in jūbako [重箱], food boxes often lacquered), nagayaki (長焼き, the eel and rice are served separately), and hitsumabushi (櫃まぶし).

There are two styles of grilled eel. One is the Kantō region

Kanto region

The is a geographical area of Honshu, the largest island of Japan. The region includes the Greater Tokyo Area and encompasses seven prefectures: Gunma, Tochigi, Ibaraki, Saitama, Tokyo, Chiba, and Kanagawa. Within its boundaries, slightly more than 40 percent of the land area is the Kantō Plain....

 Style (関東式), in which the eel is roasted first, smothered, and finally grilled with sauce. The other is the Kansai Region Style (関西式), which is grilled with sauce only. It is traditional to add sanshō (山椒, Sichuan pepper

Sichuan Pepper

Sichuan pepper is the outer pod of the tiny fruit of a number of species in the genus Zanthoxylum , widely grown and consumed in Asia as a spice. Despite the name, it is not related to black pepper or to chili peppers...

) as a condiment

Condiment

A condiment is an edible substance, such as sauce or seasoning, added to food to impart a particular flavor, enhance its flavor, or in some cultures, to complement the dish. Many condiments are available packaged in single-serving sachets , like mustard or ketchup, particularly when supplied with...

.

Unadon takes its name from the Japanese words Unagi no Kabayaki (鰻の蒲焼, literally "grilled eel") and donburi

Donburi

Donburi is a Japanese "rice bowl dish" consisting of fish, meat, vegetables or other ingredients simmered together and served over rice. Donburi meals are served in oversized rice bowls also called donburi...

(for rice bowl dish).