Muzan Kibutsuji in Demon Slayer: Kimetsu no Yaiba is voiced by Toshihiko Seki in the Japanese version and Matthew Mercer in the English dub. Both actors bring a commanding, cold menace to the role of the first and most powerful demon, capturing the character’s unsettling duality between his outwardly refined appearance and deeply cruel nature.
Toshihiko Seki (Japanese Voice Actor)
Date of Birth
June 11, 1962
About Toshihiko
Toshihiko Seki (関 俊彦) is a Japanese actor, voice actor, singer, and narrator with a career spanning from 1983 to the present. Born in Sendai, Miyagi Prefecture, Japan, he is a member of the talent agency 81 Produce and holds the rank of 2nd dan in kendo. In August 2007, Anime News Network identified him as one of the more prolific male voice actors in the industry, with 215 roles credited to his name at that time — a number that has grown considerably since.
Seki is widely recognized for his versatility, moving between characters who are intensely serious or easily agitated and those who are genuinely deranged and villainous. His gallery of iconic roles includes the earnest Iruka Umino in Naruto, the stoic Duo Maxwell in Mobile Suit Gundam Wing, and the fan-favorite Imagin Momotaros from Kamen Rider Den-O — considered his most famous role, one he has reprised across numerous productions. He was ranked the 9th favorite voice actor by readers of Animage Magazine in the 26th Annual Reader’s Poll in June 2004, largely in recognition of his performance as Rau Le Creuset in Mobile Suit Gundam SEED.
As Muzan Kibutsuji, Seki channels his experience voicing deranged antagonists to deliver a performance that is quietly terrifying. His ability to shift between a silky, composed exterior and bursts of cold fury makes him an ideal fit for the role of the Demon King. In 2025, Seki received the Best Actor award at the Seiyu Awards, recognizing his continued excellence in the craft.
Hometown
Sendai, Miyagi Prefecture, Japan
Career Highlights
- Muzan Kibutsuji – Demon Slayer: Kimetsu no Yaiba
- Momotaros – Kamen Rider Den-O
- Rau Le Creuset – Mobile Suit Gundam SEED
- Duo Maxwell – Mobile Suit Gundam Wing
- Iruka Umino – Naruto
- Kaien Shiba – Bleach
- Pluto – Pluto
- Il Dottore – Genshin Impact
Full Current Filmography
The following list reflects documented credits and may not be exhaustive.
Anime (Selected, Chronological Highlights)
- Duo Maxwell – Mobile Suit Gundam Wing
- Mousse – Ranma ½
- Iruka Umino – Naruto
- Kaien Shiba – Bleach
- Embryo – Cross Ange
- Muzan Kibutsuji – Demon Slayer: Kimetsu no Yaiba
- Pluto – Pluto (2023)
Video Games (Selected)
- William Birkin – Resident Evil series
- Muzan Kibutsuji – Demon Slayer: Kimetsu no Yaiba – The Hinokami Chronicles
- Warrior of Light – Final Fantasy series
- Il Dottore – Genshin Impact
- Chongyue – Arknights
- Scorpio Milo – Saint Seiya games
Critical Reception
Toshihiko Seki’s portrayal of Muzan Kibutsuji has been widely praised by anime fans and critics for its chilling restraint and authority. His ability to make the character feel simultaneously aristocratic and monstrous has been frequently highlighted in fan discussions on platforms such as MyAnimeList and Anime News Network, where Muzan ranks among the top fan-favorite roles in his career. His performance is often cited as one of the defining elements of the character’s on-screen presence.
Matthew Mercer (English Voice Actor)
About Greg
Matthew Mercer is a Los Angeles-based American voice actor, voice director, and music producer of Korean descent. A native of Chicago, Illinois and a graduate of Stanford University, Chun followed an unconventional path to the voice acting industry — one that included engineering work at DreamWorks, serving as musical director and conductor for a major stage musical at the former Kodak Theater, and a stint teaching computer science in graduate school. He eventually settled in Burbank, California, where he built parallel careers in music production and voice acting.
In the English-language anime world, Chun is one of the more prominent voices working today. He is perhaps best known to mainstream audiences as the English voice of Seong Gi-hun (Player 456) in the global phenomenon Squid Game, but anime fans recognize him immediately from major roles across a wide range of titles. His ability to portray characters with deep menace, quiet authority, or nuanced vulnerability has made him a go-to choice for complex leads and antagonists alike.
As Muzan Kibutsuji in Demon Slayer: Kimetsu no Yaiba, Chun brings a silky, controlled danger to the English dub that mirrors the intent of the original Japanese performance. He has voiced the character across the anime series (2019–2024) and multiple video game adaptations, establishing a consistent and recognizable interpretation of the Demon King throughout the franchise.
Hometown
Chicago, Illinois, United States
Career Highlights
- Muzan Kibutsuji – Demon Slayer: Kimetsu no Yaiba
- Garou – One Punch Man
- Thors – Vinland Saga (Netflix dub)
- Ikalgo – Hunter x Hunter
- Subtilizer / Gabriel – Sword Art Online: Alicization – War of Underworld
- Takayuki Yagami – Judgment (video game)
- Dr. Harold Winston – Overwatch (video game)
- Ike – Super Smash Bros. Ultimate (video game)
Full Current Filmography
The following list reflects documented credits and may not be exhaustive.
Anime (Voice Acting)
- Ikalgo – Hunter x Hunter
- Ryuurou Hirotsu – Bungo Stray Dogs
- Twice H. Pieceman – Fate/Extra Last Encore
- Muzan Kibutsuji – Demon Slayer: Kimetsu no Yaiba (2019–2024)
- Additional Voices – Teasing Master Takagi-san (2019)
- Additional Voices – The Disastrous Life of Saiki K.
- Subtilizer, Additional Voices – Sword Art Online (2020–2021)
- Prime Minister Zaizen – Japan Sinks: 2020
- Ethan – Dragon’s Dogma
- Youichi Aikawa – Vivy: Fluorite Eye’s Song (2021)
- Thors – Vinland Saga (Netflix dub, 2021–2023)
- Rubberball, Paragon – Super Crooks (2021)
- Alan Chen – Blade Runner: Black Lotus (2022)
- Matamune – Shaman King (2021 series)
- Noda – Ghost in the Shell: SAC_2045
Critical Reception
Matthew Mercer’s English performance as Muzan Kibutsuji has been well received by the Demon Slayer dub community, with fans praising the cold, measured authority he brings to the character. His casting has been highlighted in convention appearances and fan events — including a private signing event promoted via his official Instagram (@gregchunva) — as a fan-favorite aspect of the English dub. The announcement that the original English cast would return for Demon Slayer: Kimetsu no Yaiba – Infinity Castle (coming to US and Canadian theaters September 12) was met positively by fans, with Chun’s reprisal of the role specifically noted as a welcome confirmation.
Social Media
Matthew Mercer is active on Instagram at @gregchunva.
