Mizuho Fukushima, head of the Social Democratic Party for nearly a decade, resigned Thursday to take responsibility for the party's losses in Sunday's Upper House election and the Lower House election in December.
The SDP, whose predecessor was once the largest opposition party from 1955 to the early 1990s, won only one seat in the proportional representation segment of the upper chamber, and merely two seats in the general election in December, giving it a total Diet strength of five members.
At an executive meeting at SDP headquarters in Tokyo, Fukushima said she intended to step down as party leader and encountered no objections.