Ryomen-sukuna is a specter that was said to have appeared in Hida Province in ancient times, in the reign of Emperor Nintoku.
Ryomen-sukuna had two faces on the front and back of its head, like Janus in Roman mythology, and two pairs of arms and two pairs of legs; each pair was on the front and back of the body. The height varies from 3.03 to 54.54 meters depending on descriptions, but it was far taller than the average Japanese at that time anyway. It had a bow, arrow, and sword in its hands. It was quick-witted and had superhuman strength.
The busho (Japanese military commander) statue in the main hall of Senko-ji Temple in Nyukawa-cho, Takayama City, Gifu Prefecture (former Nyukawa-mura, Ono County) has faces on the front and back of the head while another statue with a smiling face by Enku in the same temple has an angry face on its shoulder.
According to "Nihonshoki" (Chronicles of Japan), Ryomen-sukuna appeared in Hida Province where he disobeyed the Imperial court and made people suffer, but in 377 the Imperial court sent a military commander, Takefurukuma no Mikoto, to expel Ryomen-sukuna from the province.
Benefactor of Hida Province
While "Nihonshoki" described Ryomen-sukuna as a villain and an enemy of the emperor, people in Hida and Mino Provinces treated Ryomen-sukuna as a hero and benefactor and worshipped him. Ryomen-sukuna is regarded as Kaiki (patron of a temple at its founding) of Senko-ji Temple and Zenkyu-ji Temple in Nyukawa-cho, Takayama City (former Nyukawa-mura, Ono County), and it is said that he introduced Buddhism to Hida Province. In many other old temples in Hida and Mino Provinces, Ryomen-sukuna is worshipped. Minashi-jinja Shrine, which is the ichinomiya (the highest-ranked shrine in the area) in Hida Province, has been worshipping Kuraiyama Mountain as shintaizan (a mountain worshiped as the sacred dwelling place of a deity or deities), but its enshrined deity is unknown, so a theory states that Ryomen-sukuna is a hidden deity of the shrine.
Who is Ryomen-sukuna?
One theory states that Ryomen-sukuna is a symbol of twins and brothers, therefore it refers to Oousu no Mikoto and Ousu no Mikoto (i.e. Yamato Takeru no Mikoto and his brother), twins in ancient Japanese history. Another theory states that Ryomen-sukuna refers to Emperor Chuai's sons, Kagosaka no Miko and Oshikuma no Mikoto. Both of pairs of brothers are deeply related to Mino and Hida Provinces.
Takeuchi-monjo (an ancient text which recorded the lineage of ancient kami and a dynasty preceding Emperor Jinmu) wrote Hida Province as "日玉国" or "日霊国," indicating that Hida was Takamanohara (plain of high heaven) and Kuraiyama Mountain was the Pyramid. It is considered that Ryomen-sukuna had a Hida-based dynasty the same size as the Yamato Dynasty.
Original text in "Nihonshoki"
In the year 65, there was a man in Hida Province. He was named Sukuna.
The man had a single head and torso with two faces,
Each face oriented in opposite directions. The two faces met at the top but had no nape. Each face was served by its own set of appendages. Each had knees but no ankles. He had tremendous power but still could move quickly. With two pairs of arms he held swords, a bow and an arrow.
Sukuna refused to comply with imperial directives. He threatened and plundered the people. Whereupon the emperor dispatched the founder of Wanibe no omi Naniwaneko Takefurukuma to vanquish the creature.
One of the special products of Nyukawa-cho, Takayama City (former Nyukawa-mura, Ono County) is a pumpkin called Sukune Kabocha.
Although its relevance is still unknown, it was in the news that a man-shaped haniwa (clay figure) (only its head) with two faces, on front and back, was excavated from Dainichiyama No.35 Mound (early 6th century) from the Senzuka burial mounds in Wakayama City, Kinki region. This two-faced haniwa had mizura (a hair style with the hair parted down the center and each side, left and right, tied in a figure 8), which was common among the hanima of nobility.