Shoko Arai, left, then a member of the Kusatsu town assembly, and Mayor Nobutada Kuroiwa at the assembly session on Dec. 2. A panel of the layout of the mayor’s office is placed before them. (Naohiko Izumino)

KUSATSU, Gunma Prefecture--A female assembly member here found herself the target of swift retribution after she publicly accused the mayor of sexual assault.

She was expelled from the assembly on Dec. 2 for “hurting the dignity of the assembly” with her “scandalous” remarks.

It was the first time an assembly member has been expelled in this renowned "onsen" hot spring resort town, which has a population of 6,350.

Expulsion is the most severe penalty for local assembly members under the Local Autonomy Law.

Shoko Arai said she will consider appealing the assembly’s decision to the prefectural governor.

Although there are two other precedents for the expulsion of assembly members in Gunma Prefecture over the past 30 years, the Kusatsu case marked a departure from the others in that it was voted on the same day as the motion was submitted.

Arai, 50, the only female member of the assembly, was serving her second term. She accused Mayor Nobutada Kuroiwa of groping her on Jan. 8, 2015, when she said she met him alone at his office for an hour from 10 a.m.

She leveled the accusation in an e-book, “Kusatsu Onsen Shikkoku no Yami” (Pitch-black darkness of Kusastsu Onsen) published in November, and at a news conference the same month, during which she revealed her identity and named the mayor.

In response, Kuroiwa lambasted the book for its “false content” and said he filed a complaint against Arai and the book’s 53-year-old author for libel with police in Naganohara, a neighboring town in the prefecture, which has the jurisdiction over Kusatsu.

However, police said on the afternoon of Dec. 2 that no decision had been made on whether to open an investigation into the mayor's complaint.

At the assembly plenary session on Dec. 2, Arai and a colleague submitted a no-confidence motion against Kuroiwa, citing the content of the book and asserting he is unfit to serve as mayor.

The motion was voted down, with only two in favor at the 12-member assembly.

A motion for Arai's expulsion was submitted later that day.

It accused her of making “scandalous” remarks, such as her words that she had a “sexual relationship with the mayor in his office.” The motion was carried after 10 members voted for it.

Arai told reporters afterward that she stood up to prevent a recurrence of misconduct by Kuroiwa.

“I have learned that I am not the only victim of sexual harassment committed by the mayor,” she said. “Unless somebody speaks up, others may fall victim as well. So, I raised the issue and I want him to quit as mayor.”

Kuroiwa denied her allegations during the session and contended that she should file a criminal complaint of indecent assault if she continues to insist her accusation is well-founded.

“As a man, I can declare that the possibility of my making a mistake is even below one in 130 million,” he said.

Kuroiwa acknowledged that he met Arai on Jan. 8, 2015, but only “for 15 to 16 minutes.”

The mayor asked Arai to explain where the alleged misconduct took place by bringing a panel of the layout of his office to the venue for the session.

Arai became Kusatsu’s first female assembly member in 2011. After an unsuccessful bid in the 2015 race, she returned to the assembly in the election held this spring.

In 2012, a member of the Kiryu municipal assembly in the prefecture lost her seat during an uproar triggered by a Twitter post.

But in that instance, it took 10 days to put the motion to a vote after a series of debates.