[2] In 1961 she began work as a journalist for the newspaper Asahi Shimbun, retiring in 1994 to work as a full-time social activist, founding numerous women's organizations and writing on gender inequality in Japan and on sex crimes committed by the Japanese Imperial Army, namely against the comfort women of the Second World War.

"[4] In 1961, Matsui joined the Japanese newspaper Asahi Shimbun as a reporter, writing on public health and environmental issues, such as birth defects cause by Thalidomide and mercury poisoning (Minamata disease).

[6][7] As a representative of Asahi Shimbun and of the Asian Women's Association which she founded, Matsui attended all United Nations conferences from 1975 to 1995.

[9] In 1994, she resigned from Asahi to work full-time as a social activist, her decision influenced by the trend of Southeast Asian sex tourism among Japanese businessmen.

[11] Matsui supported this idea and worked with women's rights organizations and advocates from China, Indonesia, the Philippines, Taiwan, East Timor, Malaysia, and North and South Korea in order to make the tribunal a reality.

[11] The tribunal was conducted using standard criminal trial procedures, though it held no power of law, and over 75 victims were present, with 35 former comfort women testified during the proceedings.

[12] The tribunal represented the power of civil society in terms of justice and law and showed the value of societal involvement in uncovering and preserving history, though not without criticism and attacks.

"[6][14] Even in death, she was criticized by some, Nakamiya claiming that the 1.5 million yen donated to Matsui during her illness was used selfishly by her, when, in fact, the money had been used to build the Women's Active Museum of War and Peace.