The first days of spring, summer, fall, and winter were called risshun, rikka, risshu, and ritto when the lunar calendar was used. Doyo, strictly speaking, refers to the eighteen-day periods before these four days. Today, however, doyo generally only refers to the eighteen-day period before the first day of fall. The first day of fall is called risshu in Japanese, and it falls around the 8th of August on the calendar used now. The calendar says fall begins after the doyo period, but the doyo period is the hottest time of the year. The doyo period is in midsummer. It is very humid in this season in Japan and this makes many people tend to lose their appetite and feel poorly. People often use the words natsu-bate and natsu-make, which both have the same meaning, when they want to say that they are feeling poorly in the summer. It is customary in Japan to eat eel, which is very nutritious, on a special day called ushi-no-hi during the doyo period. Since ancient times eel has been thought to provide stamina and to prevent natsu-bate (natsu-make). The day called ushi-no-hi, which is translated literally as the day of the Ox, can be seen in the calendar that follows the twelve signs of the Chinese zodiac. The twelve signs were introduced to Japan from ancient China, and they are called junishi in Japanese. The twelve signs were allocated one by one to the days on the calendar. Ushi-no-hi is the day to which the second sign of the junishi is allocated. The doyo period, which lasts for eighteen days, has one or two days designated as ushi-no-hi.
Eel is called unagi in Japanese. Many people around the world may not feel like eating eel because eel looks like snake and is slippery. Eel is valuable in Japan, however, and Japanese dishes that use eel as ingredients are very expensive. There is little eel harvested from nature, and most of the eel eaten in Japan today is raised in aqua farms. It is very difficult to prepare eel. So, people rarely cook it at home. They go to restaurants that specialize in eel when they want to eat it, or they serve ready-to-eat eel that is already cooked. It is sold at supermarkets and stores for people to eat at home. One of the most popular eel recipes is to grill the eel with a mixture of soy sauce and sugar, which is called tare in Japanese. The eel tastes particularly good when it is grilled on a charcoal fire. This recipe is called kabayaki in Japanese. The taste of eel cooked this way goes well with the taste of plain white rice. Therefore, many people prefer to eat rice with several slices of grilled eel on top. Eel liver is also used for clear soup.
The thin and wriggly shape of the eel can be compared to various things. The Japanese language has many idioms that include the word unagi (eel). One idiom is unagi-no-nedoko which literally means the lair of the eel. This refers to a house that is narrow, but long. Another idiom is unagi-nobori which means that prices, temperatures, and status rise suddenly just as if eels wriggled and swam straight upward in the water.