He first gained fame in the 1980s as vocalist of the heavy metal band Seikima-II, before starting a solo career in 1990 and branching out into other forms of entertainment.

[5][6] Demon and fellow Waseda University student Damian Hamada formed the heavy metal band Seikima-II in December 1982.

[15] His November 2019 album Uta Dokuro: Gekida☆Shinkansen Gekichūka-shū is a collaboration with the theater company Gekida☆Shinkansen, with whom he has written lyrics for and performed songs with since at least 1995.

[3] Demon collaborated with Arika Takarano (Ali Project) for the May 13, 2020 single "Jikū no Mayoi Hito" (時空の迷い人), which is the opening theme of the anime adaptation of The 8th Son?

The section, called "Ōzumō wo 666-bai Tanoshimu Hōhō" (大相撲を666倍楽しむ方法), often featured interviews with active rikishi, most notably Daitetsu Tadamitsu, who became friends with Demon.

[4] Demon was a guest commentator on day 8 of the January 2009 tournament alongside his close friend and former yokozuna Hiroshi Wajima.

[24][25] On day 2 of the January 2011 tournament Demon caused some controversy when he opined publicly on NHK that Kotomitsuki Keiji, who was expelled by the JSA in July 2010 for gambling, should be reinstated.

[26] In April 2012, Demon's alma mater Waseda University appointed him a special counselor of their sumo club which was struggling to recruit new members.

In 2017, Demon was selected by the Ministry of Internal Affairs and Communications to educate the public on and bring awareness to the harm of illegal radio waves.

[31] In February 2018, Demon took part in a symposium alongside singer Kaori Kishitani, athlete Dai Tamesue and the representative director of the Federation of Music Producers Japan speaking on the problem of ticket scalping.

[34] Demon leant his voice to Capcom's 2023 video game Street Fighter 6 as a real time commentator for fights.

When news of the cosplay spread on the internet and TV, Demon wrote a blog post stating that because it was not made clear that it was a fake, any similar acts in the future would result in legal action.