Adzuki Beans

Adzuki beans are known for being low in fat and high in vegetable protein. They also contain oligosaccharides and dietary fiber, which help regulate intestinal function, and have a high proportion of insoluble dietary fiber. These beans are also rich in potassium, which functions to excrete excess salt from the body, so adzuki are a beneficial ingredient choice when concerned about salt intake. They also contain iron, important for maintaining healthy blood, and vitamin B1, which supports carbohydrate metabolism.
As for phytochemicals, adzuki contain catechin, rutin, and saponin, which remove active oxygen, and are known to prevent lifestyle-related diseases.
Adzuki bean tea, made by roasting and boiling adzuki beans, is said to promote blood circulation and metabolism due to its saponin and potassium content, and is popular in Japan for its warming effects, especially during cold seasons.

If used up within about one year, dried adzuki beans can be stored in a cool, dark place with low humidity at room temperature. Longer storage periods will dry out these beans, and result in a longer boiling time.  In Japan, adzuki beans are sold pre-boiled with added sugar in cans or pouches, and these can be kept at room temperature for around 2 to 3 years.

Adzuki beans have been eaten in Japan for such a long time that they're even noted in Japan's oldest books from the Nara period (710-794) including the "Kojiki" (Records of Ancient Matters) and the ”Nihon Shoki” (Chronicles of Japan).  The beans used in "sekihan" (rice steamed with red beans) are actually called "sasage" (cowpea), which are similar to adzuki beans.