| 1946-10 |
Seiji Watanabe founded the exhibition decoration business in Yanaka Shimizucho, Taito-ku, Tokyo |
| 1946-10 |
Founded: October 1946 |
| 1949-10 |
The formal surviving company, Sankō Co., Ltd. (later renamed Nikki Co., Ltd.), was established in Marunouchi, Chiyoda-ku, Tokyo |
| 1949-10-14 |
Establishment / Founding: October 14, 1949 |
| 1959-12 |
Reorganized into Tanseisha Co., Ltd. (the actual surviving company) and established the current organization, headquartered in Kandanishikicho, Chiyoda-ku, Tokyo |
| 1959-12 |
Reorganized into the actual surviving company, Tansei Co., Ltd., and established the current organization: Headquarters located in Kanda Jicho, Chiyoda-ku, Tokyo |
| 1959-12-25 |
December 25, 1959: Reorganized into current organization |
| 1959-12-25 |
Establishment / Founding: December 25, 1959: Reorganized into current organization |
| 1961-11 |
Relocated headquarters to Yushima, Bunkyō-ku, Tokyo |
| 1964-02 |
Established Osaka Sales Office (registered as a branch in July 1984, now Kansai Branch) |
| 1966-09 |
Construction Business Registration (Tokyo Metropolitan Government Registration) |
| 1967-03 |
Established Tanseisha Workshop Co., Ltd. (now Tanseisha TDC Co., Ltd.) |
| 1969-05 |
Construction Business Registration (changed from Tokyo Metropolitan Government registration to Minister of Construction registration) |
| 1971-01 |
Established Sapporo Sales Office (registered as a branch in July 1984, now Sapporo Branch) |
| 1972-12 |
Established Fukuoka Sales Office (registered as a branch in July 1984, now Kyushu Branch) |
| 1974-04 |
Established Tohoku Sales Office |
| 1975-06 |
Registered as a First-Class Architect Office (registered with the Tokyo Metropolitan Government) |
| 1978-11 |
Dunyo Corporation (which changed its trade name from Nikki Corporation in July of the same year) merged with Dunyo Corporation and inherited the exhibition decoration business. Established R-B Corporation (now Dunyo Business Corporation) |
| 1978-11 |
Tansei Co., Ltd. (which changed its name from Nichiki Co., Ltd. in July of the same year) absorbed and merged with Tansei Co., Ltd., inheriting the exhibition decoration business, and established R&B Co., Ltd. (now Tansei Business Co., Ltd.) |
| 1978-12 |
Built company building in Ueno, Taito-ku, Tokyo, and relocated headquarters |
| 1983-09 |
Listed on the Tokyo Securities Dealers Association Tokyo District Association |
| 1984-04 |
Established Dunyo General Research Institute (now Dunyo Research Institute) |
| 1984-12 |
Established Nagoya Sales Office (registered as a branch in April 1989, now Nagoya Branch) |
| 1987-03 |
Listed on the Second Section of the Tokyo Stock Exchange |
| 1997-02 |
Established Dunyo Display Corporation |
| 1997-04 |
Obtained license as a real estate dealer from the Tokyo Metropolitan Government |
| 2000-03 |
Designated on the First Section of the Tokyo Stock Exchange |
| 2001-08 |
Obtained ISO 14001 certification |
| 2002-04 |
Made Game Corporation (now JDN Corporation) a subsidiary |
| 2004-03 |
Established Dunyo Human Net Corporation |
| 2006-12 |
Obtained certification for Privacy Mark use |
| 2015-09 |
Relocated headquarters to Minato-ku, Tokyo (current address) |
| 2016-04 |
Transitioned to a company with an Audit and Supervisory Committee |
| 2022-04 |
Transitioned to the |
