Black soybeans. 黒豆、くろまめ。Glycine max.
Also called "kurodaizu." The black color is caused by the presence of anthocyanin in the skin. For the rest, these beans are similar to ordinary soybeans, also as regards nutrition.
Sold in dry form, soaked, boiled and then sweetened. Most supermarkets in Japan sell them boiled and seasoned packaged in pouches or plastic trays, in other words "ready to eat."
As "nimame," (sweetened) boiled beans, they are a side dish (okazu) with rice.
They are also an important ingredient of New Year O-sechi Ryori, because of the auspicious saying "mame ni ikiru", "to have a healthy life."
The most famous black soybeans, called Tanba-kuro, come from Tanba Sasayama in Hyogo Prefecture.
Kuromame are also used (especially in the Tanba area) to make jam, coffee, tea and cocoa, as well as for flavoring ice cream.