Today is a Eel Day in Japan. It is the day you eat unagi to boost your endurance to get through a very hot summer since people believe unagi is a food that give you good stamina. The day is called “Doyo no ushi no hi (土用の丑の日, Midsummer Day of the Ox)”, and it changes depending on the Lunar Calendar. It is a day of the ox that falls within the doyo period which is supposed to be the hottest day of the year.
Unagi is not normally prepared at home since it is not easy to fillet it and also it is not easy to reproduce a sweet sauce put on unagi. People usually buy the grilled unagi with a sweet sauce at a store or go to a specialized unagi restaurant to eat. Grilled unagi is typically served on rice and some people like to sprinkle Japanese sanshō pepper on top.
I highly recommend anyone who visit Japan to eat unagi at least once, but just make sure to eat at a restaurant specialized only in unagi. It is a good sign if you can see a parson preparing unagi at a restaurant!