The Mainichi claims that it is the oldest existing Japanese daily newspaper[citation needed] with its 136-year history.

The two papers merged in 1911, but the two companies continued to print their newspapers independently until 1943, when both editions were placed under a Mainichi Shimbun masthead.

[10] On 18 September 2007, Mainichi announced the launch of their new website, mainichi.jp, which would include "heavy use of social bookmarking, RSS and blog parts" and would "pay attention to bloggers".

According to the reports, the two Japanese Army second lieutenants Toshiaki Mukai (向井 敏明) and Tsuyoshi Noda (野田 毅) were vying with one another to be the first to kill 100 people with a sword, as the Imperial Japanese Army advanced from Shanghai to Nanjing, prior to the infamous Nanjing Massacre.

[14] The Mainichi Daily News column WaiWai, by Australian journalist Ryann Connell, featured often-sensationalist stories, principally translated from and based on articles appearing in Japanese tabloids.

The column carried a disclaimer since September 19, 2002: "WaiWai stories are transcriptions of articles that originally appeared in Japanese language publications.

"[21][22] Critics had accused the WaiWai column of propagating a racist stereotype of Japanese women as sexual deviants with its sensationalist stories about incest, bestiality and debauchery.

[24] Citing continuing criticism,[25] Mainichi's Digital Media Division shut down WaiWai on June 21.

[32] Mainichi said, "We continued to post articles that contained incorrect information about Japan and indecent sexual content.

We apologize deeply for causing many people trouble and for betraying the public's trust in the Mainichi Shimbun.