Higashi is a type of wagashi

Wagashi

is a traditional Japanese confectionery which is often served with tea, especially the types made of mochi, azuki bean paste, and fruits.Wagashi is typically made from natural ingredients...

, which is dry and contains very little moisture, and thus keeps relatively longer than other kinds of wagashi.
This word can be said as the antonym of namagashi

Namagashi

are a type of wagashi, which is a general term for snacks used in the Japanese tea ceremony. Namagashi may contain fruit jellies or sweetened bean paste....

, and the definition can include rakugan, konpeito, senbei

Senbei

are a type of Japanese rice crackers. They come in various shapes, sizes, and flavors, usually savory but sometimes sweet. Senbei are often eaten with green tea as a casual snack and offered to visiting house guests as a courtesy refreshment....

, arare, and so on (though usually senbei and other alikes are not sweet and thus the word kashi/wagashi is not so fitting).

Narrower definition of higashi is ones made generally with one or more kinds of sugar

Sugar

Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

, particular sorts of flour

Flour

Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...

, and some other additives, while there are some made solely of sugars.

The flour used in higashi is usually made of rice

Rice

Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

, which has many different varieties of its own. Flours made of other ingredients, like azuki, soybean

Soybean

The soybean or soya bean is a species of legume native to East Asia, widely grown for its edible bean which has numerous uses...

 or green pea

Pea

A pea is most commonly the small spherical seed or the seed-pod of the pod fruit Pisum sativum. Each pod contains several peas. Peapods are botanically a fruit, since they contain seeds developed from the ovary of a flower. However, peas are considered to be a vegetable in cooking...

 and starches are often used too.

Those made with wasanbon

Wasanbon

Wasanbon is a fine-grained Japanese sugar, traditionally made in the Shikoku prefectures Tokushima and Kagawa. The sugar is often used for Japanese sweets . The sugar is made from thin sugarcane plants grown locally in Shikoku, called taketō or chikusha ....

, Japanese premium fine-grained sugar made with traditional method, are commonly regarded as finest ones.

The most common and well-known higashi is rakugan, but the definition of the word is somewhat vague and sometimes not suitable for a certain type of wagashi, so the word 'higashi' would be better in some cases.

Higashi are often served at Japanese tea ceremonies

Japanese tea ceremony

The Japanese tea ceremony, also called the Way of Tea, is a Japanese cultural activity involving the ceremonial preparation and presentation of matcha, powdered green tea. In Japanese, it is called . The manner in which it is performed, or the art of its performance, is called...

List of Higashi

• Goshikiitō (五色糖) - Five flavors, Bainiku (pickled ume), Hakka (Japanese mint), Nikkei (cinnamon), Shōga (ginger), and Yuzu (citron) each with distinct shapes.
• Hakusansekkei (白山雪渓)
• Hanakazura (花かずら)
• Mugirakushizuka (麦らく静)
• Nininsuzuka (二人静)
• Rakugan (落雁)
• Shigure no Matsu (時雨の松)
• Suiko (推古) - Aka (pinkish red) and Shiro (white) are available.