[2] Yamaguchi was born in London to Japanese parents, and raised in Tokyo, Japan.
[1] At the age of 15, his family moved to Melbourne, Australia, where he attended Brighton Grammar School.
[1][4] He later appeared in the film The Condemned as Go Saiga, a Japanese killer, who later teams up with McStarley.
[5] He has also acted on stage, including in Katherine Thomson's King Tide for the Griffin Theatre Company.
He holds 2nd dan black belts in judo and taekwondo, and practices kenjutsu.