Yagasaki Zentaro has already conducted a series of research on Izyuin Kanetune. In these researches, it became clear about the late life when Izyuin was active as the Suki-mono, but the footsteps of the first half of "modern engineers" are not yet clear. In addition, Yagasaki used "Koikokaishin-roku" of Kuroda Tengai and "Meiji-kako-tyo" when showing Izyuin, but there are also multiple other records and articles of interviews with him. Therefore, this paper presented the report on Izyuin by Yagasaki, and examined the matters in the first half when Izyuin was active in the government and business circles, in particular, the purpose is to clarify the relationship between the Doboku-kentiku-gumi, the Nihon-doboku-kaisya and Izyuin. The Doboku-kentiku-gumi was also known as the construction of the Rokumeikan designed by Condor. The following points were clarified, focusing on the first half when Izyuin was active in government and business circles.

 Izyuin built the Zisin-no-ma in a residence in Kagoshima as a teenager. He also constructed a steam bath for six days and was dispatched to Edo as the reward. In 1868 at Bosin-no-eki, he served as the military detective in Edo, and he was dispatched to Oshu, then he sent the injured to Yokohama and bought the weapon. Izyuin worked as the Goyo-kakari of Kanagawa Prefectural from May to November 1868, and once returned to Kagosima, he moved to Tokyo again and opened a kimono store. His work at the Miyauchi Office was from 1871 to 1872 and his service to the Navy was from around 1872 to 1887, and work at the Ministry of Industry until around the end of 1878. After he retired from the government, he belonged to the Doboku-youtasi-gumi and built the Rokumeikan. Izyuin who was closely related to Ookura Kihachi through the Doboku-youtasi-gumi, took office as Tokyo resident accountant when the Nihon-doboku-kaisya was established in 1887. And Izyuin was also related to the Sangu-tetudou-kaisya, Iris Co., Dai-Nihon-seihun, Tokyo-gekizo-kaisya and so on. As the diplomat, he sold arms to the Army at Okuragumi in 1889-94. As his houses, Nakahashi-Suzuki-cho, Shibata-cho 8-chome, Shiba-Isarako-tei, Sakyragawa-tei, Kamakura's villa in later years, and the residence of Shiba Park which was the end of the land are newly confirmed.