# Toshihiko Seki (関俊彦)
**Toshihiko Seki** (関俊彦, born 1962) is a Japanese voice actor, stage actor, singer, and narrator affiliated with the talent agency 81 Produce. He is known for long-running roles such as Doi Hansuke in *Nintama Rantaro*, Genjyo Sanzo in the *Saiyuki* series, and Momotaros in the tokusatsu (Japanese live-action genre heavy on special effects, like Power Rangers) series *Kamen Rider Den-O*, and for villain roles including Muzan Kibutsuji in *Demon Slayer: Kimetsu no Yaiba* and Rau Le Creuset in *Mobile Suit Gundam SEED*.[1](https://www.81produce.co.jp/actor_search/index.php/item?id=64) • [2](https://anime.eiga.com/person/10909/)
| Key fact | Detail |
|---|---|
| Born | 1962, Moka, Tochigi Prefecture, Japan[3](https://jimbutsu.jitenon.jp/jimbutsu/p16162.php) |
| Agency | 81 Produce[1](https://www.81produce.co.jp/actor_search/index.php/item?id=64) |
| Debut | 1983, radio drama *Hana no OH-EN Magic*; first anime lead as JJ in *Red Photon Zillion* (1987)[4](https://www.fashion-press.net/profiles/47281) • [2](https://anime.eiga.com/person/10909/) |
| Signature roles | Doi Hansuke (*Nintama Rantaro*, from 1993), Genjyo Sanzo (*Saiyuki*), Momotaros (*Kamen Rider Den-O*), Duo Maxwell (*New Mobile Report Gundam Wing*), Muzan Kibutsuji (*Demon Slayer*)[2](https://anime.eiga.com/person/10909/) • [4](https://www.fashion-press.net/profiles/47281) |
| Awards | 2nd Seiyu Awards Synergy Award (Kamen Rider Den-O); 15th Seiyu Awards Kei Tomiyama Award; 19th Seiyu Awards Best Lead Actor[1](https://www.81produce.co.jp/actor_search/index.php/item?id=64) |
| Music | More than 200 songs released; "Climax Jump DEN-LINER form" from *Kamen Rider Den-O* debuted at No. 2 on the Oricon chart[5](https://tmaa.ac.jp/specialguest/seki01/) • [2](https://anime.eiga.com/person/10909/) |
| Specialty | Kendo, second dan[1](https://www.81produce.co.jp/actor_search/index.php/item?id=64) |
## Early life and training
Seki was born in Moka, Tochigi Prefecture, and attended Tochigi Prefectural Moka High School before entering the economics department of Komazawa University.[3](https://jimbutsu.jitenon.jp/jimbutsu/p16162.php) He belonged to the kendo club through middle school and high school, describing the high school training as particularly rigorous; he later held a second-dan rank in kendo.[5](https://tmaa.ac.jp/specialguest/seki01/) • [1](https://www.81produce.co.jp/actor_search/index.php/item?id=64)
His path into acting began at university, when he joined an acting class run by the actress Natsuko Kawaji, wanting to do something different from kendo. As the voice-acting share of the agency's work grew, he began receiving voice roles.[5](https://tmaa.ac.jp/specialguest/seki01/) An interest in acting also came from an older sister who loved the theater; on entering university he became an apprentice of the theater troupe Group Chaos, initially aiming to be a stage actor, before a connection with an instructor led him to join 81 Produce.[4](https://www.fashion-press.net/profiles/47281)
## Career
**Debut and early roles.** Seki debuted as a voice actor in 1983 with the radio drama *Hana no OH-EN Magic*, while still a student at Komazawa University.[4](https://www.fashion-press.net/profiles/47281) • [2](https://anime.eiga.com/person/10909/) His first job was a soldier in NHK's *The Mysterious Cities of Gold* (Taiyō no Ko Esuteban), a single line of being speared and falling, delivered more than a dozen times; the director told him he sounded like nothing but a bird call.[5](https://tmaa.ac.jp/specialguest/seki01/) His first starring role in a television anime came in 1987 as JJ in *Red Photon Zillion*.[2](https://anime.eiga.com/person/10909/) In the early years most of his parts were background characters, and he has said he encourages young performers to take crowd work seriously because someone always notices a good improvised line.[5](https://tmaa.ac.jp/specialguest/seki01/)
**Breakthrough roles.** In *YAWARA!* he played Matsuda Kōsaku, a newspaper reporter following the protagonist, a role he has named as an unforgettable one that spread his name.[4](https://www.fashion-press.net/profiles/47281) From 1993 he has voiced the ninja-school teacher Doi Hansuke in *Nintama Rantaro*, a role he continued for more than 30 years, including the 2024 theatrical film *Nintama Rantaro: Dokutake Ninja-tai Saikyō no Gunshi*.[4](https://www.fashion-press.net/profiles/47281) • [6](https://webnewtype.com/report/cast/entry-32558.html) He voiced Duo Maxwell in *New Mobile Report Gundam Wing* and Genjyo Sanzo in the *Saiyuki* series.[2](https://anime.eiga.com/person/10909/)
**Momotaros and Den-O.** In the tokusatsu series *Kamen Rider Den-O* (2007–2008) he voiced Momotaros, the Imagin who possesses the protagonist and becomes the title rider's partner.[4](https://www.fashion-press.net/profiles/47281) The opening theme "Climax Jump DEN-LINER form", sung with his co-performers, debuted at No. 2 on the Oricon chart, and CDs released from the series became a social phenomenon; at the 2nd Seiyu Awards (for 2007), the four performers including Seki received the Synergy Award.[2](https://anime.eiga.com/person/10909/) • [5](https://tmaa.ac.jp/specialguest/seki01/)
**Range of roles.** Commentators describe his range as running from handsome, earnest characters such as Duo Maxwell and Doi Hansuke, through villains such as Rau Le Creuset in *Mobile Suit Gundam SEED*, to rough, violent characters such as Senketsu in *Kill la Kill* and Momotaros.[2](https://anime.eiga.com/person/10909/) In *Demon Slayer: Kimetsu no Yaiba* he plays Muzan Kibutsuji, the progenitor of the demons, a role he won through an audition after studying the original manga; he has said he continues to audition throughout his career and treats a rejection as a mismatch with the requested character rather than a judgment on himself.[4](https://www.fashion-press.net/profiles/47281) Other roles include Iruka Umino in *NARUTO*, Pluto in *PLUTO*, and Heisuke Higuchi in *[Shōwa Genroku Rakugo Shinjū](https://www.edgepedia.org/descending-stories-showa-genroku-rakugo-shinju)*.[1](https://www.81produce.co.jp/actor_search/index.php/item?id=64) In games he has been credited on 145 titles, including Rau Le Creuset in the *Gundam SEED* games, Muzan Kibutsuji in *Demon Slayer: Kimetsu no Yaiba – Sweep the Board!*, and Orgodemir in *Dragon Quest VII: Reimagined*.[7](https://www.mobygames.com/person/215533/toshihiko-seki/credits/)
**On-camera and narration work.** As a live-action presenter he appeared on NHK's educational program *Fue wa Utau* as the "flute oniisan" for eight years.[5](https://tmaa.ac.jp/specialguest/seki01/) His profile lists narration and dubbing among his regular genres alongside anime and games.[3](https://jimbutsu.jitenon.jp/jimbutsu/p16162.php)
## Music and stage
Seki has a reputation as a singer and has released more than 200 songs.[5](https://tmaa.ac.jp/specialguest/seki01/) In 1991 he formed the unit Banana Fritters with Noriko Hidaka and [Koichi Yamadera](https://www.edgepedia.org/koichi-yamadera); after a hiatus the unit resumed activity in 2016.[4](https://www.fashion-press.net/profiles/47281) On stage he co-ran the theater company Dramatic Company with Ryūsei Nakao, acting in its productions and directing performances by younger members until the company dissolved in 2022.[4](https://www.fashion-press.net/profiles/47281)
## Awards
The 81 Produce profile lists three Seiyu Awards: the Synergy Award at the 2nd Seiyu Awards for *Kamen Rider Den-O*, the Kei Tomiyama Award at the 15th Seiyu Awards, and the Best Lead Actor Award at the 19th Seiyu Awards.[1](https://www.81produce.co.jp/actor_search/index.php/item?id=64) The 19th Seiyu Awards, honoring the most active voice performers of 2024, were announced on March 15, 2025; Seki received the Best Lead Actor Award and said he regarded it as an award shared with Hideyuki Kiuchi, who played Mizuki alongside his Father of Kitaro in *Kitaro Birth: The Mystery of GeGeGe* (2023).[6](https://webnewtype.com/report/cast/entry-32558.html) In his acceptance interview he cited the film's success, which brought him promotional work, exhibitions, cinema concerts, and events through 2024.[6](https://webnewtype.com/report/cast/entry-32558.html)
## Acting approach
In a lecture to high school students aiming at voice-acting careers, Seki argued that simply speaking naturally does not work through the filter of animation: a performance needs exaggeration and deformation grounded in reality, comparing a kendo master's authentic sword handling, which would lack dramatic force, with a trained actor's convincing stage combat that explains the story's situation.[5](https://tmaa.ac.jp/specialguest/seki01/) He has also described the craft as a lifelong alternation between difficulty and enjoyment, and credits the actor Chikao Ōtsuka, his co-star on *Nintama Rantaro*, with teaching him to attend to a character's gestures and wordless moments rather than displaying technique.[5](https://tmaa.ac.jp/specialguest/seki01/) • [4](https://www.fashion-press.net/profiles/47281)
## References
1. [関 俊彦 – 81プロデュース profile](https://www.81produce.co.jp/actor_search/index.php/item?id=64)
2. [関 俊彦：声優情報 – アニメハック (Anime!Anime!)](https://anime.eiga.com/person/10909/)
3. [関俊彦（声優）のプロフィール – 人物事典](https://jimbutsu.jitenon.jp/jimbutsu/p16162.php)
4. [関俊彦のプロフィール・経歴・出演映画 – ファッションプレス](https://www.fashion-press.net/profiles/47281)
5. [関 俊彦 – 東京声優・国際アカデミー special guest interview](https://tmaa.ac.jp/specialguest/seki01/)
6. [「第十九回 声優アワード」主演声優賞・関俊彦インタビュー – WebNewtype](https://webnewtype.com/report/cast/entry-32558.html)
7. [Toshihiko Seki – Video Game Credits – MobyGames](https://www.mobygames.com/person/215533/toshihiko-seki/credits/)
---
*Topic: Encyclopedia › Arts and culture › Screen and stage › Film and television › Screen people and creators › Voice performers › Japanese voice performers › Surnames N to Y*
*Initially written Sep 17, 2026 · Reviewed: Sep 18, 2026; Oct 25, 2026 · Edited: Sep 18, 2026; Oct 12, 2026; Oct 25, 2026 · Last review: Oct 25, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license