Mari Kotani

In 2003, she established the annual Kotani Cup "for celebrating the best cos-players at Japanese National SF Convention."

Kotani is one of the founders of the Japanese Sense of Gender Award (equivalent to the Tiptree Award) in 2001, and of The Japanese Association of Feminist Science Fiction and Fantasy. She is now the chair of the Japan PEN Women Writers Committee and a member of the Science Fiction Writers of Japan.

In 1997, Media Works published a reference book, Alternative Culture, which contained an article describing Kotani's book, Evangelion as the Immaculate Virgin, and depicted Mari Kotani's name as a pseudonym for her husband Takayuki Tatsumi, a professor of English at Keio University. When her complaints were ignored, she sued the author of the entry (Hiroo Yamagata), the publisher and Shufu-no-Tomo-sha, the distributor of the book, for what she termed "textual harassment." The lawsuit was broadly supported by Japanese writers. The Japan PEN Club established a Women Writer's Committee, with feminist critic Kazuko Saegusa as chair, and Kotani as sub-chair. During this period, Kotani and Maki Honda's translation of Joanna Russ' How to Suppress Women's Writing received by major feminist critics in Japan including Chizuko Ueno, Fukuko Kobayashi, Yuko Matsumoto, and Kazuko Takemura. In 2001 the defendants were ordered to pay Kotani 3,300,000 yen (roughly $27,500), and to publish an apology on the top page of their respective website.

Kotani was not the first cosplayer in Japan but she is the earliest documented instance of cosplay at a fan event in that country. She attended a costume party at the 17th Nihon SF Taikai (also known as "Ashinocon") science fiction convention in 1978 wearing a costume based on the cover art for Edgar Rice Burroughs' novel A Fighting Man of Mars. This costume has sometimes been misreported as a Triton costume (from the manga Triton of the Sea) due to its visual similarity and because Kotani was known at the time as a member of the TRITON fan club. She was one of about the twenty people at the event wearing a costume; the others were either members of the same Triton of the Sea fan club or of Kansai Entertainers (西芸人人, Kansai Geinin), the antecedent of the Gainax anime studio. Despite being a costume party, most attendees wore ordinary clothing.

Mari Kotani (小谷 真理, Kotani Mari, born in Toyama Prefecture on July 11, 1958) is a Japanese science fiction critic, best known as the author of Evangelion as the Immaculate Virgin (analysis of the anime serie Neon Genesis Evangelion), Tokyo: Magazine House, 1997 and of Joseijou muishiki: techno-gynesis josei SF-ron josetsu, Tokyo: Keiso shobo, 1994 (Techno-Gynesis: The Political Unconscious of Feminist Science Fiction), which won the 15th Nihon SF Taisho Award.