| Jan 2011 | Minister of Defense (2nd Reshuffled Kan Cabinet) |
| Sep 2010 | Minister of Defense (Reshuffled Kan Cabinet) |
| Jul 2010 | Elected as a Member of the House of Councillors (4th term) |
| Jun 2010 | Minister of Defense (Kan Cabinet) |
| Sep 2009 | Minister of Defense (Hatoyama Cabinet) |
| Aug 2007 | Vice President of the Democratic Party of Japan (DPJ)
Chairman, Committee on Foreign and Defense at the House of Councillors |
| Jul 2004 | Elected as a Member of the House of Councillors (3rd term)
Chairman, Committee on Fundamental National Policies at the House of Councillors |
| Oct 2002 | Vice Chairman, the Assembly of DPJ Members of the House of Councillors |
| Aug 2001 | Chairman, Committee on Land and Transport, at the House of Councillors |
| Aug 2000 | Secretary General, the Assembly of DPJ Members of the House of Councillors |
| Aug 1998 | Chairman, Diet Affairs Committee, the Assembly of DPJ Members of the House of Councillors |
| Jul 1998 | Elected as a Member of the House of Councillors (2nd term) |
| May 1993 | Parliamentary Vice Minister of Agriculture, Forestry and Fisheries at Hada Cabinet |
| Jul 1992 | Elected as a Member of the House of Councillors (1st term) |
| 1975 | Elected as a Member of Nagano Prefectural Assembly (5 terms) |
