One of the greatest Zen masters of the 900th century, he studied under the masters of the Rinzai and Soto Zen traditions, receiving transmission in both lineages. Harada Daiun Sogaku revived the practice of Koan Zen at the heart of the Soto Zen School. He was born in Obama City (Fukui Prefecture) on October 13, 1871. On April 8, 1883, Harada Roshi was ordained as a Soto Zen Monk by Harada Sodo Roshi, Master of the Bukkoku-Ji Temple, and received Dharma transmission on the 8th March 1895. He studied at Soto-shu Daigakurin (now Komazawa University) and graduated in 1901. After graduation, he studied Zen with many Soto masters, such as Akino Kodo Roshi, Oka Sotan Roshi, Hoshimi Tenkai Roshi, Adachi Tatsujun Roshi and Rizai masters such as Unmuken Taigi Sogon Roshi (Master at Ibuka Shogen-Ji) and Kogenshitsu Dokutan Sosan Roshi (Master at Kyoto Nanzen-Ji).
From 1911 until 1923, Harada taught at Soto-shu Daigakurin.

He became Master of the Hosshin-Ji Monastery in 1924 and subsequently of the Chisai-in, Ankoku-Ji, Hoon-Ji, Chigen-Ji Monasteries. In 1937 he retired into a hermit while he was Master of the Chigen-Ji Monastery and lived in the Kakusho-ken temple. He died at the age of ninety on December 12, 1961 in Kakusho-ken.
Many of the best-known Zen Masters in the West descend directly or indirectly from his lineage: Yasutani Roshi, Maezumi Roshi, Aikten Roshi, Tetsugen Glasmann Roshi, Daido Loori Roshi, Tetsugen Serra Roshi.

Harada Daiun Sogaku was one of the few Masters officially recognized by all as "Master of the two schools Soto Zen and Rinzai Zen".

Ban Tetsugyu Soin was ordained as a Soto Zen monk in 1917 in Fuchizawa, by the master Engaku Chimyo, from whom he would later receive the transmission of the Dharma. From 1931 to 1938 he practiced at Hossin-ji, which was led by master Harada, from whom he probably learned the method that combined the practice of koans with the forms of the Soto tradition. He later became a student at Komazawa University, where he graduated in 1941.

In 1947 he became Tanto, the second position in the monastery after the master, in Hosshin-ji monastery. The following year, he held the same position at the Rinzai Hoon-ji monastery in Kyoto. In the same year, he received Dharma Transmission from Master Harada, and became abbot of Soto Tosho-ji Monastery in Tokyo. Subsequently, he founded the Kannon-ji monastery in Iwate and the Tetsugyu-ji in Oita.

Tetsugyu Soin was one of the first Japanese Zen masters to open his doors to Western disciples who wanted to approach his teaching. The case of the nun Maura Soshin O'Happellon became particularly famous, as she wrote about her years spent at Tosho-ji monastery in her diary Pure Heart, Enlightened Mind. Other similar cases worthy of note are that of the American Paul Tesshin Silverman, who, succeeding Tetsugyu Soin as abbot of Tetsugyu-ji, became the first Western abbot of a Japanese monastery in 1993, and of the Italian Carlo Zendo Tetsugen Serra, who brought as a missionary his teachings in Italy, founding the Enso-ji monasteries in Milan and Sanbo-ji in the province of Parma.

Tetsugyu Soin retired as abbot of Tosho-ji in 1992, leaving his position to heir Tetsujyo Deguchi, current abbot of the Tokyo monastery. He died four years later, again in the Japanese capital, at the age of eighty-seven.