The DPJ was not experienced in governing but it was remarkable in many aspects, he said. He called on the voters to continue to support the DPJ so the reform plan outlined by it could be carried on.
All polling stations will close by 08:00 p.m. local time and vote counting will begin immediately after that. Full results are due out by Monday morning.
The upper house has 242 seats, of which 96 are elected by proportional representation from a national constituency and 146 are elected from Japan's 47 prefectures. Councilors' term of office is six years.
The upper house holds elections every three years for, alternately, only half of the total 242 seats, with the other half remain uncontested until the next election. The upper house is not subject to dissolution, meaning that elected officials are basically guaranteed a full term of six years.