For many people who never had sushi before or couldn't get well with fish, this is an entrance dish to open the door graciously. Unagi Don is the abbreviation of unagi donburi, eel in a rice bowl. The name explains the whole dish already. Very simple, straightforward to anyone.
Unagi don is composed by two things, eel and rice. The eel is usually grilled in kabayaki style, similar to teriyaki. The fillets will be pinned together via bamboo sticks and then put on the charcoal fire to grill. After it is cooked for a while, the fillets will be taken off the grill for the worker to remove the fishbones. Probably steamed for a while. Then, the fillets will be dipped and glazed with a sweetened soy-based sauce, to be tare and caramelized. After that, they can be put back to the grill for finishing. (more details Momentum.Travel's video https://youtu.be/dn88LiPOKMc)
The fillets are not flayed, and the grayish skin side is placed faced down on top of the rice. Sufficient tare sauce will be poured into the rice and also make the skin sticky to the rice underneath. Sometimes, thing egg roll pieces or sesames will be put between the fillet and the rice, or sprinkled over to add flavors.
Good or bad fillets can be identified once you put them onto the grill. When burning the fat, good fillets will generate an attractive aroma but bad ones may not smell anything. Eels are the most popular and most expensive fish in Japan. The strong flavor from the sauce covers the fish smell that some people cannot accept. It is an easy to try dish and easy to fall in love with dish for everyone.
Depending on the vessel to carry the final dish, unajū (鰻重) is eel rice served in jūbako (重箱), food boxes often lacquered; Nagayaki (長焼き) is to have the eel and rice served separately; and hitsumabushi (櫃まぶし), eel and rice together but served with other condiments. It is to put 1/4 of hitsumabushi eel rice to the empty smaller bowl and mix it with other condiments to enjoy portion by portion.
Una-don was the first type of donburi rice dish, invented in the late Edo Period, during Bunka era (1804-1818) by Imasuke Ōkubo, a of Sakai-machi, nowadays Nihonbashi Ningyōchō, Chūo-ku, Tokyo. There are several famous eel rice restaurants in Tokyo area. Except for the one mentioned in the video, 神田 きくかわ 日比谷店(帝国劇場内) is a hidden treasure right across the palace. Hopefully, if you have never had sushi or don't like fish yet, this will open the whole new world for you!