Nakai started playing shogi at the age of 4. She finished second in the in 1981 at the age of 11. In 1983, she entered the Japan Shogi Association's apprentice school and reached the rank of 2-kyū before deciding to leave in 1990.
Shogi professional
Nakai was awarded the rank of women's professional 2-kyū by the Japan Shogi Association in April 1981 at the age of 11 as a protegee of. In 1993, Nakai became the first women's professional to defeat a regular professional in an official game when she beat in a Ryūō tournament game. Nakai was 16 years old when she won her first major title in 1985 by defeating the reigning Women's MeijinNaoko Hayashiba three games to one to win the title. The following year the roles were reversed with Nakai successfully defending her title against the challenger Kobayashi three games to two. In 2003, Nakai became the first women's professional to win a NHK Cup TV Shogi Tournament game. She won her round 1 game of the 53rd NHK Cup against Mamoru Hatakeyama and then in round 2 won against Teruichi Aono. She lost in round 3 to Makoto Nakahara. The following year Nakai also qualified for the 54th NHK Cup and beat Shūji Satō in round 1. In round 2, Nakai faced Yasumitsu Satō who was the reigning Kisei title holder. Nakai obtained an advantageous position against Satō, but was unable to convert it into a win. Nakai is still the only women's professional to have won a NHK Cup game. In April 2009, Nakai became the first women's professional to win 500 official games, and then became the first women's professional to win 600 official games in January 2015. In August 2010, Nakai defeated Sayuri Honda in the quarterfinals of the to win her nineteenth official game in a row and set a new record for consecutive wins by a women's professional.
Nakai is married to retired shogi professional. The couple have three daughters. She served as a member of the Warabi, Saitamaboard of education from 2003 to 2015 and was named a "Warabi City PR Ambassador" in May 2016.
Nakai has appeared in major title matches a total of 43 times and has won a total of 19 titles. She has won the Women's Meijin title nine times and has been awarded the title of. She has also won the title four times, the title three times and the Kurashiki Tōka Cup three times. In addition to major titles, Nakai has won 17 other shogi championships.
Major titles
Other championships
Note: Tournaments marked with an asterisk are no longer held or currently suspended.
Awards and honors
Nakai received a number of Japan Shogi Association Annual Shogi Awards and other awards in recognition of her accomplishments in shogi and contributions made to Japanese society.
Annual shogi awards
13th Annual Awards : Women's Professional Award
14th Annual Awards : Women's Professional Award
16th Annual Awards : Women's Professional Award
20th Annual Awards : Women's Professional Award
27th Annual Awards : Women's Professional Award
29th Annual Awards : Women's Professional of the Year
30th Annual Awards : Women's Professional of the Year
31st Annual Awards : Women's Professional Award
22nd Annual Awards : Women's Professional Award
38th Annual Awards : Women's Professional Most Games Played
40th Annual Awards : Women's Professional Most Games Played