What are real black beans like?

Round, bigger ones should be real black beans, which belong to black-skinned soybeans; The flatter and smaller one should be black adzuki bean, which belongs to a kind of adzuki bean.

To be more specific: black beans are relatively large, and they are green when opened; Black adzuki bean is smaller, but larger than other adzuki beans (red adzuki bean and white adzuki bean), and has the same shape as other adzuki beans, except that the skin is black and the inside is white when broken.

A large number of adzuki beans are planted in the north of Heilongjiang Province.