In 1830 (Bunsei 13), he was born as the eldest son of Yoshii Sahei of Nakamura, Yamabe District, Kazusa Province (Togane City, Chiba Prefecture).

　He became the adopted son of Confucian scholar Seki Shunsuke, entered the school of Sato Taizen of Sakura, and studied medicine. He opened a practice in Choshi, but by the recommendation of Hamaguchi Goryo, he mastered Western medicine under Pompe in Nagasaki.
　
　After that, he was invited by the Tokushima Domain and became a samurai doctor, but in the Boshin War, he was active as the Director of the Ou Branch Hospital, and poured his efforts into the establishment of the Tokushima Medical School, etc. For a time, he served at the Naval Hospital and made achievements as the 2nd generation director of Yamanashi Prefectural Hospital, but after returning to Tokushima Prefecture, he returned both his stipend and status and opened a practice at the Higashi Goten Ato (Former East Palace Site) (Tokushima-cho 1-chome, current Joto High School), devoted himself to community medicine, and the path leading to Seki Clinic was called Seki no Koji (Seki's Alley) by the people of Tokushima.

　After receiving the celebration of the Kansai couple's golden wedding anniversary, he aspired to the development of Hokkaido, which was noted as a necessary land for Japan's industrial development. At that time, he was already 70 years old, and his fourth son Mataichi was enrolled in Sapporo Agricultural College. It was in 1902 (Meiji 35), at the advanced age of 72, that he pioneered the Ishikari Tarukawa Farm and further settled in the land of Toma, Tokachi Province, which was a remote area.
He sought a policy of pioneering for the cultivation of independent farmers at Ninomiya Farm, managed by Ninomiya Sonshin, and formed the Sekizensha society. Also, he deepened his friendship with Tokutomi Roka, and aimed for resonance with Tolstoy's philosophy and the construction of an ideal rural village, but it was in the autumn of his 82nd year that he entrusted his aspirations to his sons Yosaku and Mataichi and ended his own life.