By one theory, the rock art discovered in 1866 in Temiya Cave actually consists of written characters.
These carvings in Otaru are relics of the continuing Jōmon culture which persisted in the region from the 3rd century BC until the 7th century AD, when it was replaced by Satsumon culture.
In 1921, they were designated a national historical landmark.
They became public knowledge after an 1878 investigation conducted by Enomoto Takeaki, the secretary of the Kaitakushi (Hokkaido Development Commission) Yamanouchi Teiun, and the British geologist John Milne.

In October 1913, the archaeologist Torii Ryūzō contributed an article to Volume 22, Issue 4 of Historical Geography (歴史地理) entitled Concerning Carved Letters in Temiya, Hokkaido (北海道手宮の彫刻文字に就て).
He claimed that the letters were in the old Turkic alphabet, representing a Tungusic languages used by the Mohe people.
Moreover, the linguist Nakanome Akira contributed an article to the 71st issue of Shōko (尚古), published in February 1918, entitled Ancient Turkic Letters Preserved in Our Country (我国に保存せられたる古代土耳其文字).
Adopting Torii's Turkic theory, he claimed to have deciphered the carvings in Temiya Cave, and that in the Mohe language they read: "... We led our subordinates across the great sea ... we fought ... we entered this cave ..." In that month's Otaru Shinbun newspaper, Nakanome asserted that the Mishihase people subjugated in the Nihon Shoki by Abe no Hirafu were in fact Mohe people, and that Temiya Cave is the ruins of the burial place of their chief, who died in the conflict.

On the other hand, in 1944, the local historian Fumihiro Asaeda published The Ancient Letters of Otaru (小樽古代文字), in which he propounded a theory that the carvings in Temiya Cavern represented ancient Chinese hanzi.
By his theory, they were made by people of the Zhou dynasty court, and record that a fleet dispatched on an expedition was visiting the area when the "emperor" (帝) who led them died and was buried.
After some calamity occurred, the Zhou held a bloody ritual.
He further conjectured that ships from Shang and later Zhou China frequently visited Hokkaido to obtain deer antlers for use in rituals.

In 1972, Asaeda published a further work in which he indicated three more items he believed to contain characters of the same type.
He supposed that all of these were ancient records of ceremonies conducted for the dead.

The jindai moji researcher Tatsuo Sōma offered another theory in 1978, when he published Reading Japan's Ancient Scripts (解読日本古代文字, Kaidoku Nihon Kodai Moji).
He argued that the carvings in Temiya Cave were made by members of a group of people chased from the Hokuriku region by another group of originating in Baekje.
He also shared his interpretations of the meanings of the carvings; Unoke, Noto, Kaga, and the other places he refers to by name are all located in modern Ishikawa prefecture.

Destroy our enemies.
We entered this cave to use it as a base.
Store up military might.
Our gods will kill our enemies without fail.

— Sōma, Tatsuo.
 解読日本古代文字 [Reading Japan's Ancient Scripts] (in Japanese).
p. 21.

Attack!
At Unoke, and Noto and at Ouchi in Kashima in Kaga, and at Nono and Kaga in Kaga.
Smash the barriers and important areas and divide them.
Strike at Kaga, captured by our foes, shoot through Hakui and Wajima, good lands where the brutes now gather, and set them afire.
Noto, which pokes into the sea; how beautiful our birthplaces, Unoke on the plain of Kaga, Nono, Kaga.

— Sōma, Tatsuo.
 解読日本古代文字 [Reading Japan's Ancient Scripts] (in Japanese).
p. 22.
By one theory, the rock art discovered in 1866 in Temiya Cave actually consists of written characters. These carvings in Otaru are relics of the continuing Jōmon culture which persisted in the region from the 3rd century BC until the 7th century AD, when it was replaced by Satsumon culture. In 1921, they were designated a national historical landmark. They became public knowledge after an 1878 investigation conducted by Enomoto Takeaki, the secretary of the Kaitakushi (Hokkaido Development Commission) Yamanouchi Teiun, and the British geologist John Milne.
In October 1913, the archaeologist Torii Ryūzō contributed an article to Volume 22, Issue 4 of Historical Geography (歴史地理) entitled Concerning Carved Letters in Temiya, Hokkaido (北海道手宮の彫刻文字に就て). He claimed that the letters were in the old Turkic alphabet, representing a Tungusic languages used by the Mohe people. Moreover, the linguist Nakanome Akira contributed an article to the 71st issue of Shōko (尚古), published in February 1918, entitled Ancient Turkic Letters Preserved in Our Country (我国に保存せられたる古代土耳其文字). Adopting Torii's Turkic theory, he claimed to have deciphered the carvings in Temiya Cave, and that in the Mohe language they read: "... We led our subordinates across the great sea ... we fought ... we entered this cave ..." In that month's Otaru Shinbun newspaper, Nakanome asserted that the Mishihase people subjugated in the Nihon Shoki by Abe no Hirafu were in fact Mohe people, and that Temiya Cave is the ruins of the burial place of their chief, who died in the conflict.
On the other hand, in 1944, the local historian Fumihiro Asaeda published The Ancient Letters of Otaru (小樽古代文字), in which he propounded a theory that the carvings in Temiya Cavern represented ancient Chinese hanzi. By his theory, they were made by people of the Zhou dynasty court, and record that a fleet dispatched on an expedition was visiting the area when the "emperor" (帝) who led them died and was buried. After some calamity occurred, the Zhou held a bloody ritual. He further conjectured that ships from Shang and later Zhou China frequently visited Hokkaido to obtain deer antlers for use in rituals.
In 1972, Asaeda published a further work in which he indicated three more items he believed to contain characters of the same type. He supposed that all of these were ancient records of ceremonies conducted for the dead.
The jindai moji researcher Tatsuo Sōma offered another theory in 1978, when he published Reading Japan's Ancient Scripts (解読日本古代文字, Kaidoku Nihon Kodai Moji). He argued that the carvings in Temiya Cave were made by members of a group of people chased from the Hokuriku region by another group of originating in Baekje. He also shared his interpretations of the meanings of the carvings; Unoke, Noto, Kaga, and the other places he refers to by name are all located in modern Ishikawa prefecture.
Destroy our enemies. We entered this cave to use it as a base. Store up military might. Our gods will kill our enemies without fail.
— Sōma, Tatsuo.  解読日本古代文字 [Reading Japan's Ancient Scripts] (in Japanese). p. 21.
Attack! At Unoke, and Noto and at Ouchi in Kashima in Kaga, and at Nono and Kaga in Kaga. Smash the barriers and important areas and divide them. Strike at Kaga, captured by our foes, shoot through Hakui and Wajima, good lands where the brutes now gather, and set them afire. Noto, which pokes into the sea; how beautiful our birthplaces, Unoke on the plain of Kaga, Nono, Kaga.
— Sōma, Tatsuo.  解読日本古代文字 [Reading Japan's Ancient Scripts] (in Japanese). p. 22.
Hokkaido characters