He is best known for his role as Chozen Toguchi in the film The Karate Kid Part II (1986) and its sequel television series Cobra Kai (2021–present).

He has also appeared in the films Better Off Dead, Real Genius (both 1985), True Believer (1989), American Yakuza (1993), Contact (1997), The Truman Show (1998), Pearl Harbor (2001), Only the Brave (2006), Inception (2010) and Driven (2018).

[4] Other credits include his role as Shu Kai Kim, a character based on Chol Soo Lee, in the 1989 film True Believer, Pete Kapahala in the 1999 Disney Channel original movie Johnny Tsunami, Japanese navy lieutenant (海軍大尉, Kaigun-Daii) Zenji Abe in Pearl Harbor, and Bruce Takedo in the television series, Bones.

[4] In 2005, he was Yukio Nakajo in Lane Nishikawa's film Only the Brave about the Japanese American segregated fighting unit, the 442nd Regimental Combat Team of World War II.

[5] In 2021, Okumoto reprised his Karate Kid II role as Chozen Toguchi, who, beginning with Season 3 of Cobra Kai, is now a friend and ally of Daniel.