Komainu are statues of stone (or sometimes metal or jade) which may take the shape of a lion, a dog or a wolf, though sometimes the creature it is meant to represent ends up being a strange mix of all of those. They may also have horns (usually one or two) on their forehead.
The most frequent variant of the komainu theme, though, is the fox. Often one, and sometimes both, has a sûtra roll, a key or a jewel in its mouth. (Sūtras are Buddhist texts). The statues do not stand for the malice the animals are proverbial for, but for the magic powers they are believed in this case to possess. Sometimes the guardians are painted, and in that case they are always white, which is a "holy" color. Although visible genitals are rare, the left fox is believed to be male, the right one female.
They are fierce guardians who protect territories - usually Shrines - with a dedication rarely seen anywhere else. Komainu are loyal to no end and will put their lives at risk if it means doing their job right.
Of Chinese origins and meant to ward off evil spirits, most komainu statues are almost identical, though one has an open mouth, the other closed. This is a very common characteristic in religious statue pairs at both temples and shrines.
They are said to rarely, if ever, leave the area they are protecting. Some legends tell of Komainu coming to life at night to fight the spirits that may be trying to cause mischief in the shrine they protect.
It is also said that they will get a life of their own only when they reach a hundred years old and may live as long as they aren't shattered completely.