He was born the eldest son of the Takamiya family, poor farmers in Tateoka village in Dewa Province, now Murayama in Yamagata. His childhood name was Motokichi; some accounts give 1755 as his birth year. Helping the family by peddling tobacco across northern Japan, he kept studying on his own.
After his father died the year before, he left the family trade to his younger brothers, though he was the eldest, and went to Edo to pursue learning. Working as a servant in the house of Yamada Tonan, a shogunate physician, he studied medicine and mathematics, a bold choice for a poor farmer's son.
He entered the Otowa school of Honda Toshiaki, versed in astronomy, surveying and foreign affairs. Toshiaki was a political economist who stressed foreign trade and northern development, and Tokunai learned his ideas along with surveying techniques. He also went to Nagasaki to train in mathematics.
Under senior councillor Tanuma Okitsugu, the shogunate planned a survey of Ezo. Recommended in place of his ailing teacher Toshiaki, he joined the expedition in the lowly role of a laborer. With Aoshima Shunzo and others he surveyed from Kushiro to Nemuro and, guided by the Ainu chief Ikotoi, crossed to Kunashiri.
He wintered in Matsumae, crossed again to Kunashiri and went on with Ikotoi to Etorofu and Uruppu. On Etorofu he met Russians and, with Ainu as go-betweens, learned about Russia. That year, however, Tanuma fell from power and the development of Ezo was halted.
The year before he had tried again to go to Ezo, but the Matsumae domain discovered who he was and expelled him. He settled in Noheji in Mutsu, relying on a boatman named Shinshichi, and married Fude, daughter of the Shimaya, a merchant house in brewing and shipping.
The Kunashiri-Menashi uprising of the Ainu broke out in Ezo, and Tokunai informed Aoshima in Edo. He went with Aoshima to investigate, but on their return the two were suspected of overstepping their duties and imprisoned. Aoshima died of illness in prison.
Tokunai also fell ill in prison, but thanks partly to his teacher Toshiaki's efforts he was found innocent and released. Valued for his experience and ability, he was then appointed a fushinyaku official of the shogunate, an exceptional rise for someone of farming origin.
On shogunate orders he went to survey Sakhalin, studying its geography and noticing the Matsumae domain's smuggling and harsh treatment of the Ainu. On the previous trip to Ezo he had also taught the Ainu how to grow crops and ordered trading scales to be standardized. As an official expert on Ezo, he was sent north again and again.
In a large shogunate survey of Ezo he went to Etorofu under Kondo Juzo and erected the marker reading Dai Nippon Etorofu to claim the island for Japan. He also led road building through the Hidaka mountains, but clashed with the expedition's leader and was removed from the post.
As tensions with Russia rose, he was posted to Sakhalin and crossed from Soya. He traveled from Aniva Bay in the south around to the west coast and saw Santan boats sailing to and from the mainland. In all he went to Ezo nine times and was known as the foremost expert on the region.
He visited the German physician Siebold, who had come to Edo, and met him many times to discuss the north and scholarship. He showed him a map of Sakhalin surveyed by Mamiya Rinzo and helped his study of the Ainu language. He is said to have been one of the Japanese Siebold trusted most.
He spent his last years in Asakusa, Edo, and died this year. His book Ezo Soshi, describing northern geography, Ainu life and Russian affairs, became known worldwide through Siebold. He also remained a lifelong friend of the nativist scholar Hirata Atsutane.
Tanuma OkitsuguHirata AtsutaneMamiya RinzōPhilipp Franz von Siebold
Tsutaya JūzaburōUesugi YōzanDaikokuya KōdayūKitagawa UtamaroŌtsuki GentakuRyōkanMatsudaira SadanobuKatsushika Hokusai
People of the Edo period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.