October 1946Founded by Masaji Watanabe (Yanaka, Shitaya-ku).
December 1959Reorganized as Tanseisha Co., Ltd. Headquarters established (Kanda, Chiyoda-ku).
November 1961Headquarters completed (Yushima, Bunkyo-ku).
February 1964Osaka office established (currently the Kansai branch).
September 1966Registered as contractor (Tokyo Gubernatorial Registration).
March 1967Tanseisha Kosakusho Co., Ltd. founded (currently Tansei TDC Co., Ltd.).
May 1969Registered as contractor (changed to Ministerial Registration).
January 1971Sapporo office established (currently the Sapporo branch).
December 1972Fukuoka office established (currently the Kyushu branch).
April 1974Tohoku office established.
June 1975Registered as an office of a first-class architect (Tokyo Gubernatorial Registration).
November 1978Tansei Business Co., Ltd. founded.
December 1978Headquarters completed (Ueno, Taito-ku).
September 1983Over-the-counter shares registered with the Japan Securities Dealers Association.
April 1984Tansei Information Institute Co., Ltd. founded (currently Tansei Institute Co., Ltd.).
December 1984Nagoya office established (currently the Nagoya branch).
March 1987Shares listed on the Second Section of the Tokyo Stock Exchange.
February 1997Tansei Display Co., Ltd. founded.
April 1997Obtained the Real Estate Trader License (Tokyo Gubernatorial Registration).
March 2000Shares listed on the First Section of the Tokyo Stock Exchange.
August 2001ISO14001 certification acquired.
April 2002Game Co., Ltd. (currently JDN Inc.) becomes subsidiary.
June 2003TANSEI CREATIVE DESIGN CO., LTD. (Shanghai, P.R.China) founded.
March 2004Tansei Humanet Co., Ltd. founded.
August 2005Beijing Tansei Co., Ltd. founded.
October 2006T&T Co., Ltd. founded.
December 2006Obtained Privacy mark usage permit.
September 2015Headquarters completed (Konan, Minato-ku).
April 2016Transitioned to a company with audit and supervisory committee.