The Japanese doughnut filled with sweet red bean paste is called an-doughnut.
An-doughnuts are fried pastries filled with anko, a sweet paste usually made from azuki beans. The name combines “an,” referring to the bean filling, with “doughnut,” identifying the Western-style fried pastry form.
The filling distinguishes an-doughnuts from plain ring doughnuts and from Japanese sweets such as dorayaki, which are soft bean-filled pancakes. Taiyaki is also commonly filled with anko, but it is cooked in a fish-shaped mold rather than fried as a doughnut.
An-doughnuts show how Japanese confectionery adapted an internationally familiar format to a traditional local flavor. They are commonly sold in bakeries and sweet shops, where red-bean-filled pastries are widely popular.