Renho, a Democratic Party member from Tokyo, retained her seat in a landslide victory in Sunday's Upper House election.

The 48-year-old acting president of the largest opposition force was elected to her third term, it was announced soon after polls closed at 8 p.m. Her re-election, however, was bittersweet after the party's overall poor performance.

"The DP still has numerous problems, but we are working on them one by one," Renho said. "We were often told that we were not united, but the party is now undivided."

Renho — an ex-swimsuit idol turned TV journalist who first won a seat in the Upper House in 2004 — shot to stardom in Japan in 2009 as a member of a government committee tasked with screening budget requests by ministries. She was known for waging fierce battles with bureaucrats.

Renho, who goes by just one name, was floated as a candidate in this month's Tokyo gubernatorial election but passed on the chance, saying her interests remain in national politics.