According Japanese traditions, Koma inu are noble holy animals which are usually employed as guardians of holy areas. They can range in size from a small dog to the size of a lion, and due to their resemblance to both creatures, are often called lion dogs in English. They have thick, curly manes and tails, powerful, muscular bodies, and sharp teeth and claws. Some koma inu have large horns like a unicorn on their heads, however many are hornless.

Koma inu are fierce and noble beasts. They act like watchdogs, guarding gates and doorways and preventing the wicked from entering. They live together in male-female pairs, and are always found together. In their pairs, the female usually guards those living inside of the place they guard, while the male guards the structure or place itself.

Koma inu are a ubiquitous symbol at holy places in Japan. Stone koma inu statues are almost always found at the entrance to Shinto shrines, often with more inside the shrine guarding the important buildings. The pairs are usually carved in two poses: with mouth open, in a roaring position, and with mouth closed. Symbolically, these creatures represent yin and yang, or death and life. The open-mouthed koma inu represents "a", while the closed-mouthed koma inu represents "un". These sounds are the Japanese transliteration of the Sanskrit "Om", a mystical syllable which symbolizes the beginning, middle, and end of all things. A western analogy would be alpha and omega.

Koma inu were brought to Japan via Korea, which in turn received them from China, which in turn received them from India. China is where they first began to symbolize the dharmic philosophics of Indian religions. In China, these dogs are called shishi, which means "stone lion". This name is often used in Japan, too, though it only refers to the left one (the one with its mouth open). The right one and the two of them collectively are always referred to as koma inu.