About Anko:
Anko, or an, is sweet bean paste which is usually made of azuki (red beans). It's often used to make traditional Japanese sweets. The term, an, has a wide range of meanings in Japanese cooking. An indicates fillings in dumplings, sauce thickened by starch, and so on. Anko made of azuki beans is also called azuki-an.
Anko Varieties:
Mainly, there are two types of anko: tsubu-an and koshi-an. Anko without bean skins is koshi-an, and tsubu-an includes bean skins. Anko made of white azuki or kidney beans is called shiro-an. Tsubuan is also called ogura-an.