A woman with Down syndrome on Sunday cast a ballot in Ibaraki Prefecture for the Upper House election thanks to a recent revision of the Public Offices Election Law that permits adults assisted by a guardian to vote.

After visiting a polling station near her home in Ushiku, Takumi Nagoya, 50, said: "I had intensive practice so I could write the name of a candidate. . . . I'm glad that I could vote."

Nagoya's father, Seikichi Nagoya, 81, was named her guardian in 2007. Since then, she had been unable to vote, as a now-defunct provision in the election law that stripped adults of their voting rights if they required help from a guardian.

Nagoya filed a lawsuit against the state in 2011, arguing the provision was unconstitutional. The Tokyo District Court ruled in her favor this March.

The government then reached a settlement with Nagoya and three other plaintiffs in similar cases before the House of Councilors election, and the election law was revised in May.

"We have finally reached this point. I'm full of emotion," Seikichi Nagoya said after casting his vote Sunday with his daughter and wife, Keiko, 80.

According to Supreme Court data, around 136,000 adults had been assigned guardians as of the end of 2012.