Milestone
| 1919 | Jun. | Establish in Ueno-village, Chita-county, Aichi (Current Nawa-machi, Tokai-city) |
| 1941 | Dec. | Reorganize (Capital 198,000 yen) |
| 1948 | Apr. | Start dredging (Horikawa river dredging) |
| 1954 | Mar. | Build a wooden grab dredger (1 RYOSEI MARU) |
| 1957 | Sep. | Move office to current location |
| 1959 | Mar. | Build a steel grab dredger (10 RYOSEI MARU) |
| 1963 | Mar. | Increase the capital to 18,000,000 yen |
| 1967 | Apr. | Open Tokyo branch |
| 1970 | Jun. | Build an anchorless grab dredger (61 RYOSEI MARU) |
| 1975 | Mar. | Patent anchorless moving equipment (2 Spuds) |
| Nov. | Increase the capital to 36,000,000 yen | |
| 1984 | Jul. | Open Osaka branch |
| 1985 | Sep. | Build a hydraulic counter weight balance system grab dredger (261 RYOSEI MARU) |
| 1988 | May. | Increase the capital to 80,800,000 yen |
| 1993 | Jul. | Build an air pressure transfer vessel (Air pressure vessel) (AP 1000 RYOSEI MARU) |
| 1995 | Jul. | Build a mega grab dredger (200m3 Grab bucket) TOSHO |
| 2000 | May. | Build a second mega grab dredger (200m3 Grab bucket) GOSHO |
| 2004 | Aug. | GOSHO & TOSHO complete Nakayama channel dredging |
| 2008 | Oct. | First overseas dredging project in Saudi Arabia (GOSHO) |
| 2012 | Apr. | First African dredging project in Republic of South Africa (TOSHO) |
| Sep. | Increase the capital to 90,000,000 yen | |
| 2014 | Jun. | First South East Asian dredging project in Singapore (661 RYOSEI MARU) |