Unadon or Unagi-donburi (a bowl of boiled rice topped with broiled eel) (鰻丼)

Unadon, or unagi-donburi, is a Japanese cuisine consisting of boiled rice in a bowl topped with kabayaki (broiled eel) and poured tare (a special sauce for broiled eel) on it, and as one's preference, some powdered sansho (Sichuan pepper) added on top.

Summary
Sansho pepper is believed to be effective in helping digestion. It also removes the muddy smell and makes the taste of fatty eel rather simple to eat. Tare sauce for unadon or unagi-donburi is mainly made from soy sauce and sugar, but its ingenious recipe is traditionally and secretly reserved in each shop. Usually, the tare sauce is first poured on the plain boiled rice and then poured again after the broiled eel is placed on it. Sansho powder may be sprinkled on top at the end.

History
According to "Zokuji Hyakko Kigen (1885) Masayasu MIYAGAWA" (literally, the "Origins of Mundane Affairs and Crafts and Arts written in 1885 by Masayasu MIYAGAWA,"), unadon (or unagi-donburi) was said to have been devised by Imasuke OKUBO in Sakai-cho (the present-day Ningyo-cho, Tokyo). The taste of boiled rice with the tare sauce seeped in it became so popular in the Shibai-cho area, and it is said that Onoya in Fukiya-cho as the origin started selling it under the catch phrase, "Ganso Unagi-meshi" (the originator of a dish of broiled eel on boiled rice).

Unagi-meshi is an abbreviation for "unagi donburi meshi (a bowl of boiled rice topped with broiled eel)," according to Morisada Manko (a kind of encyclopedia of folkways and other affairs in the Edo period, written by Morisada KITAGAWA), which is regarded as a basic document on the history of early modern folkways. Prior to the Meiji period, the term "donburi (bowl)" meant "unagi donburi." Also, in those days, waribashi (splittable wooden chopsticks) were introduced. Even today, the term "unagi meshi" is used in some shops and areas.

The difference between unadon (or unagi-donburi) and unaju

Unaju is an abbreviation for "unaju don." The dish contained in jubako (tiered food boxes) is called unaju. Occasionally, the dish is called unaju when broiled eel and boiled rice are served in a double layer ("ju 'pile-up'", in such an alternate order from the bottom, as rice-eel-rice-eel). Kimosui (a clear soup with eel guts) is often served along with it. The jubako box made its appearance during the Taisho period, and lacquer or other material was used in an effort to create the impression of luxury, so that even today unaju in a jubako box tends to be more expensive than unadon or unagi-donburi in a bowl.

Remarks
The broiled-eel dish has been a specialty of Lake Hamana and its surrounding area, since the cultivation of eel was once the prosperous industry of the area.

Previously, "unagi-bento" (a box lunch containing broiled eel, commonly known as "una-ben") used to be sold on the Tokaido Shinkansen (and partly on the Sanyo Shinkansen), but that is no longer the case.