Being a model, Koyuki is better known as a Japanese actress through her roles on Japanese television and in several Japanese films like Pulse (2001), Laundry (2002) and Alive (2002). She gained her first exposure to Western audiences in Edward Zwick's 2003 film The Last Samurai (2003). She also appeared in Blood: The Last Vampire live-action film (2009) starring Jun Ji-hyun, where she plays Onigen, the arch-villain. For her work, she was nominated a Japan Academy Prize for Outstanding Performance by an Actress in a Leading Role.
Regarding of her model career, after winning a an exclusive modelling contract with the magazine Non-no in 1997, she grew quickly in this area from then on.
In 2011, she got married to actor Kenichi Matsuyama, who co-starred with her in Kamui Gaiden, with two children.