In Japan, Nio is two fearsome, muscular, wrath-filled, protectors of Buddha known as Ungyo and Agyo found at temple gates. You will notice that one has its mouth open and the other has its mouth closed if you look at their mouths, said to represent life and death, the beginning and the end. At the entrance gate of the Tōdaiji temple in Nara, the most famous Niō in Japan can be found. Threatening appearance and The Niō's fierce is said to ward off evil spirits and keep the temple grounds free of demons and thieves. The Niō were said to have followed and protected the Historical Buddha when he traveled throughout India in some accounts. Since they have adopted the Japanese into the Japanese Buddhist pantheon. They represent two aspects of Vairocana (Dainichi Nyorai), In Esoteric Buddhism. They are sometimes confused in this respect with the wrathful forms of Fudo Myoo and Aizen Myoo. Although similar to these latter forms they are distinct from them. They traveled with Gautama Buddha to protect him and there are references to this in the Pāli Canon as well as the Ambaṭṭha Sutta, According to Japanese tradition and are Dharmapala manifestations of the bodhisattva Vajrapāṇi, the oldest and most powerful of the Mahayana Buddhist pantheon.

Stories of Dharmapala's justified the use of physical force to protect cherished values and beliefs against evil, within the general pacifist tradition of Buddhism. There is a wide range of styles for Nio Like other forms of Buddhist art in Japan. By highly ranked artists some were created and have been repaired and renovated and sometimes freshly painted. Except for traces others have virtually no paint left, and yet others display layers of peeling that show earlier renovations. Some of the Nio quite crude but quite expressive, made by folk artisans, but no matter their pedigree or age, Nio always come in pairs, and, like the komainu, one will have an open mouth, the other closed.
Agyo: is the open-mouthed one is making the "a" sound. This represents birth. In an expression of absolute violence, he bares his teeth. Either he holds a weapon, clenches his fist, or both.
Ungyo: With a shut mouth which said to represent death and an open palm Ungyo is always depicted. Ungyo radiates strength.
The meaning of word Nio is "Benevolent Kings" and some stories say they traveled with and protected the historical Buddha. It is also known as Kongo Rikishi and Shukongoshin. nio, are known as Misshaku Kongo and Naraen Kongo alternatively. They are believed to be Hindu deities, Vajra Dahra, thunderbolt holders, incorporated into Buddhism as protectors Like their Chinese and Korean counterparts,

In Japan, The oldest extant examples known are from Horyu-Ji Temple in Nara and are dated 711. the pair found at Todai-Ji Temple in Nara, towering 26 ft in height, they date from 1203 are Probably the most famous one. By the Zen monk Suzuki Shōsan (1579–1655) Nio Zen Buddhism was a practice advocated, who advocated Nio Zen Buddhism over Nyorai Zen Buddhism. The Niō (Vajrapani) is a menacing God. Around the 8th century, The Nio guardians were introduced to Japan. They originate from Hindu deities who were adopted by the Japanese into Buddhist teachings. There once was a king who had two wives, According to another Japanese mythology. His first wife bore a thousand children who all decided to become monks and follow the Buddha's law and second wife had only two sons.

Non-O was the youngest helped his monk brothers with their worship. To be the first of the heavenly kings Kongo Rikishi is considered, called Nio. Stories of Nio guardians like Kongo Rikishi justified the use of physical force to protect the cherished values and beliefs against evil, within the general pacifist traditions of Buddhism. According to Japanese conception, Kongo Rikishi used to ride a mythical creature called Karura, very similar to Garuda, the magical bird from Ramayana in Indian mythology. The Nio is also referred to as Misshaku Kongo & Naeren Kongo in other records. Representing power in action, Misshaku Kongo bares his teeth and raises his fist in action, while Naeren Kongo, representing potential might, holds his mouth tightly closed and waits with both arms tensed but lowered.