Demon and fellow Waseda University student Damian Hamada formed the heavy metal band Seikima-II in December 1982. The band saw numerous lineup changes in their career, with Demon being the only constant member. They signed to CBS/Sony and released their first album "Seikima II – Akuma ga Kitarite Heavy Metal" in 1985. Seikima-II went on to release 12 studio albums and sell over 10 million records. In accordance to their fictional "prophecy" and after completing their "world conquest", Seikima-II disbanded at the end of the century on December 31, 1999 at 23:59:59. They have had limited time reunions in 2005, 2010, and 2015.