Masumi was born in 1754 as Shirai Hideo, in the countryside outside of Nagoya (Mikawa province). For reasons which remain largely unknown, he left on a journey in 1783, possibly intending from the very beginning to make his way to the island of Ezo (today known as Hokkaidô). After much traveling, in 1788 he finally found his way across the Tsugaru Strait, to Ezo, where he remained for four years, attempting to learn the language of the Ainu, and to assemble an Ainu-Japanese dictionary. He returned to Honshû (Tôhoku), spending his remaining years in what is today Akita prefecture (i.e. parts of Dewa and Mutsu provinces), never returning south to Edo or Nagoya.
It is unclear if he ever met with other now prominent travelers, such as Furukawa Koshôken, who spent time in Tôhoku at the same time as Masumi was there; however, on several occasions, Masumi took note in his writings of preparations for an official group which scholars surmise was that with which Koshôken was traveling.
In his later years, he attempted to chart the complete topography of this area, a project he never completed. Masumi died in 1829, leaving numerous diaries full of waka poetry, paintings, and descriptions in great detail of people and places. Less gullible, that is, more skeptical than Tachibana Nankei, but not as dismissive of local legends as Furukawa Koshôken, Masumi has been described as simply recording things he saw and heard, without passing judgement; he includes in his diaries, for example, mentions of a rock he is told was supposedly sat on by Shinran, and of trees supposedly planted by Ono no Komachi, but he makes no further comment about these. Masumi is said to have never written with the intention of publishing; he was more than happy to produce manuscript copies for friends, but never submitted to a publisher (of course, it would have been difficult to do so, since he never returned to central Japan). Before he died, though, Masumi did donate many of his works to the Meitokukan, a domain school in Akita.
His writings were collected and published in 1966 as Sugae Masumi yûranki ("Records of the Travels of Sugae Masumi").
- Amino Yoshihiko, Alan Christy (trans.), Rethinking Japanese History, Center for Japanese Studies, University of Michigan (2012), 124n3.
- Bolitho, Harold. "Travelers' Tales: Three 18th Century Travel Journals." Harvard Journal of Asiatic Studies 50:2 (1990). pp485-504.
- Wittkamp, Robert. "Between Topos and Topography: Japanese Early Modern Travel Literature." in Asian Crossings: Travel Writing on China, Japan and Southeast Asia. Hong Kong University Press, 2008. pp15-29.