Kenyū Horiuchi is a veteran Japanese voice actor and narrator born on July 30, 1957, in Gotenba, Shizuoka Prefecture. He is the founder and representative director of his own talent management agency, Kenyu Office, which he established in 2002. Horiuchi began his career in 1983, with his debut role in the tokusatsu series Andromelos. Prior to founding his own office, he was affiliated with Production Baobab.

His voice is characterized as having a calm, sincere, and resonant quality, allowing him to portray a wide array of characters, from handsome and earnest heroes to cool-headed, villainous, and comedic roles. In his later career, he has frequently taken on mature and elderly characters. He is also the official Japanese dubbing voice for several major Hollywood actors, including Brad Pitt, Charlie Sheen, Ben Affleck, and Ben Stiller. Notably, he received personal approval from Brad Pitt for his Japanese voice-over work.

Horiuchi has an extensive filmography in anime, spanning several decades. Some of his most recognized television anime roles include Pain and Nagato in Naruto Shippūden, Kin'emon in One Piece, Professor Oak and the narrator in the Pokémon anime (a role he took over in late 2018), and Wilhelm van Astrea in Re:Zero - Starting Life in Another World. He also plays Ō Sen in the series Kingdom, as mentioned in the prompt. His work in the Gundam franchise is notable, with early roles such as Mashymre Cello in Mobile Suit Gundam ZZ and Jamil Neate in After War Gundam X, and he also appears as Demnar Kitako Jr. in Mobile Suit Gundam: Iron-Blooded Orphans – Urðr Hunt Special Edition. Other significant anime roles include Sanson in Nadia: The Secret of Blue Water, Grencia Mars Elijah Guo Eckener in Cowboy Bebop, Hokushin in Yu Yu Hakusho, Takamura Mamoru in Hajime no Ippo: The Fighting!, En in Dorohedoro, and the Second Hokage, Tobirama Senju, in the Naruto series.

Beyond anime, Horiuchi is highly active in video games and dubbing foreign films. In video games, he is known for voicing Raiden in the Metal Gear Solid series and Zhuge Liang in several installments of the Dynasty Warriors series. His dubbing work is extensive, having provided the Japanese voice for characters in numerous live-action films and TV series, such as Sam Wheat in Ghost, Rick O'Connell in The Mummy, Jerry in Seinfeld, Han Solo in the Star Wars films, and Kronk in The Emperor's New Groove.

Throughout his career, Horiuchi has built recurring collaborations, particularly within the Neo Romance series of games and events, where he voiced the character Oscar in the Angelique franchise. He was the only voice actor to have played a character in all three major Neo Romance series and was celebrated for making one hundred appearances at live Neo Romance events. He also maintains a long-standing personal and professional friendship with fellow voice actor Jūrōta Kosugi, his former high school classmate, with whom he co-hosts a live talk event.

For his contributions to the voice acting industry, Kenyū Horiuchi received the Kei Tomiyama Award at the 6th Seiyu Awards in 2012, which recognizes a voice actor for their body of work.