Another elder sister of independent House of Representatives member Takeshi Tokuda pleaded guilty Thursday to illegally helping her brother's election campaign in 2012.

Narumi Koshizawa, 50, allegedly provided cash or airline tickets worth ¥150 million to employees of the Tokushukai hospital group in a bid to make them join Tokuda's campaign in the December 2012 general election.

At the start of her trial at the Tokyo District Court, however, Koshizawa's lawyers stressed her limited involvement in allegedly breaking the Public Offices Election Law, saying she did not issue direct instructions for rewarding group employees.

Koshizawa's two suspected conspirators pleaded not guilty at the trial, while her younger sister, Michiko Stern, 46, pleaded guilty last month.

On Wednesday, prosecutors on Stern's case demanded a 30-month prison term as the session closed. The district court is expected to hand down a ruling on Stern on March 5.

Tokuda, a third-term Lower House member, left the Liberal Democratic Party in November after his relatives were arrested.