|Born||22 August 1980|
Kawasaki, Kanagawa, Japan
(m. 2006; div. 2014)
Her father is Ikuei Yamamoto, who also competed in the Olympics as a wrestler. Her older brother is mixed martial artist Norifumi Yamamoto. Her sister Miyuu Yamamoto is female wrestler and mixed martial artist who won three world titles and one Asian Wrestling Championship in her career.
In four years from 1999 till 2003, she collected four gold medals at the World Wrestling Championships. Because she lost at the Japan Queen's Cup to Saori Yoshida, she was unable to participate at the 2004 Summer Olympics. In 2006 she married team handball player Hideaki Nagashima and later retired, and in 2007 gave birth to a son. Two years later she came back and won another championship at the Poland Open.
- "Nagashima Yamamoto, Seiko". International Wrestling Database. Retrieved 16 July 2013.
- Charles Jewett (April 3, 2013). "Seiko Yamamoto Interview". Asian MMA. Retrieved July 9, 2013.
- "Yamamoto Ikeda, Miyu". International Wrestling Database. Retrieved 25 July 2018.
- Shu Hirata (January 7, 2009). "A Former World Wrestling Champ Seiko Yamamoto, KID Yamamoto's Sister, Making a Comeback Aiming for London in 2012!". Retrieved July 9, 2013.
- "Rangers wish Yu Darvish well after pitcher welcomes new baby" by Michael Florek Dallas News (July 2015) August 3, 2017
- "Yu Darvish, Rangers highly anticipating return to action" by Jerry Crasnick (February 22, 2016) ESPN August 3, 2017
- "東京スポーツ プロレス大賞：選考経過（1990～1999）". Tokyo Sports (in Japanese). Retrieved December 16, 2017.
- "東京スポーツ プロレス大賞：選考経過（2000～2009）". Tokyo Sports (in Japanese). Retrieved December 16, 2017.