Osaka Mayor and Nippon Ishin no Kai (Japan Restoration Party) chief Toru Hashimoto plans to sue the weekly Shukan Asahi and daily Asahi Shimbun, claiming they violated his human rights when the magazine ran an article six months ago touching on his family background.

"Freedom of the press and freedom of expression are the basis for democracy, so I've been quiet. Since becoming a public official, I've respected press freedom. But I'm taking legal procedures against Shukan Asahi," Hashimoto tweeted Saturday.

Last October, the magazine ran a cover story by a freelance nonfiction writer who noted Hashimoto's father had been a member of the yakuza and came from an area in Osaka traditionally associated with descendents of the "burakumin" feudal-era outcasts. The article was supposed to be the start of a series exploring Hashimoto's rise.