Masayuki Yamaguchi was born on January 3, 1961, in Nagano Prefecture, Japan.

[2] While in high school, he was inspired to enter the animation industry after seeing Hayao Miyazaki's 1978 anime series Future Boy Conan.

[3]: 96 In 1982, Masayuki worked on "Key Animation" in several OVA and television anime, including: Acrobunch,[4] Cream Lemon,[5] Fist of the North Star,[6] Cream Lemon Part 4: POP CHASER,[7] Bavi Stock,[8] Gunbuster,[9] Doomed Megalopolis,[10] and Neon Genesis Evangelion.

[11] He has also worked under the pseudonym Wase Emishi (夷 倭世, Emishi Wase), on some media, including: Macross Plus,[12] Macross Plus: Movie Edition,[12] and Re: Cutie Honey.

[12] Masayuki is a close friend of the famed Neon Genesis Evangelion creator Hideaki Anno.