1931 ･Founded "Sanjo Kozai" in Iizuka-cho, Takasaki City, the first president Hoshiyuki Arai predecessor 1964 ･Established Togun Kozai Co., Ltd. and opened Isesaki Sales Office in Yanagihara-cho, Isesaki City 1969 ･Opened inventory center in Higashikaminomiya-machi, Isesaki city. 1972 ･Opened Takasaki Sales Office in Minamioorui-machi, Takasaki City 1974 ･Capital increased to 30 million yen and became the current capital 1980 ･Constructed a new head office and warehouse in Tamamura-machi, Sawa-gun, Gunma, and integrated Isesaki and Takasaki sales offices 1985 ･Changed head office location to 1413-2 Kaizawa-machi, Takasaki City 1989 ･Construction of a processing plant on the premises of the head office and advance to primary processing of shaped steel 1994 ･Misako Arai appointed as Representative Director 2001 ･Appointed as Akio Arai, Representative Director ･Automatic shaped steel processing line certified as Gunma Prefecture one company one technology 2015 ･Daisuke Arai appointed as Representative Director 2016 ･New introduction of groove processing machine for short column 2017 ･Base material / product yard installed on company land adjacent to the head office ･Updated column processing line (up to 40 x 800 size can be supported) ･Introduced second groove processing machine for short columns, newly introduced small band saw for shaped steel 2018 ･Updated H-section steel NC 6-axis high-speed drilling machine to the latest machine and automated carry-in / carry-out conveyor 2019 ･Updated the unit worker to the latest machine, introduced the latest model of the shaped steel punching and cutting compound machine, and expanded the yard of the head office. ･Opened Tamamura Kita Factory in Tamamura-machi, Sawa-gun, Gunma Prefecture, and relocated one combined drilling and cutting machine ･The office was renewed and the sales management system was converted to the cloud. ･Renovation of head office and implementation of sales management system in cloud ･Introduced H-shaped steel groove processing machine and scaler for shaped steel at Tamamura Kita Factory 2020 ･Introduced a large-scale multi-function machine for H-shaped steel drilling and cutting at the Tamamura Kita Factory
･Opened Tochigi No. 1 Factory, Tochigi No. 2 Factory, and Tochigi Sales Office in Tochigi City, Tochigi Prefecture.