Two of her major works, The Three Hagi Sisters (萩家の三姉妹, Hagi-ke no san shimai) and Time's Storeroom (時の物置, Toki no mono oki), both exemplify her utilization of realism.
Examples include Jūrō Kara's Jōkyō Gekijo, Makoto Satō's [ja] Kuro Tento and Ren Saitō's Jiyū Gekijō.
After graduating in 1974, Nagai was invited to join the theater company, Spring and Autumn Group (Shunjūdan), where she met Shizuka Ōishi.
Nitosha has consistently provided plays that do not only entertain the audience but also make them feel actually involved and committed to the issues presented on stage.
Examples include the immediate aftermath of Japan's defeat in World War II, the high-growth period of Japanese economy, and the final period of campus riots in 1970 against the renewal of the Japan-U.S. Security Treaty The trilogy consists of these three plays: Time's Storeroom (時の物置, Toki no mono oki), in which she depicts the first half of the 1960s; Daddy's Democracy (パパのデモクラシー, Papa no demokurashī), in which she depicts the period immediately after World War II; and My Tokyo Diary (僕の東京日記, Boku no Tokyō Nikki), in which she depicts life in the early 1970s.
Nagai also connects Time's Storeroom (時の物置, Toki no mono oki) to another social change, the abolition of legal prostitution in 1958.
This adaptation confronts current feminist issues and brings to light the disparity between traditional expectations of men and of women.
It is a social comedy depicting the Tokyo Board of Education's decision in 2003, in which teachers are punished if they fail to abide by the ruling to raise the flag and sing the national anthem at graduation ceremonies.
The casts included Keiko Toda, Ryosuke Otani, Moeko Koyama, Masami Nakagami, and Yoshimasa Kondo.
The play's English translation was developed by Kyoko Yoshida and Andy Bragen in late 2007 at The Playwrights' Center in Minneapolis, Minnesota.
This is one of her plays that was read in front of an audience and featured American actors led by Cynthia Croot, a New York City theater director.
[5] Three of her highly evaluated works, Daddy's Democracy (パパのデモクラシー, Papa no demokurashī), Brother Returns (兄帰る, Ani kaeru), and Men Who Want to Make Them Sing (歌わせたい男たち, Utawasetai otoko-tachi), portray contemporary Japanese lives satirically.
Nagai and another playwright, Hisashi Inoue, have similarities in their approaches because they both aim to write about ordinary people going through extraordinary situations.