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Susumu Hirasawa, who did the music for the anime and the DC game, composed Sign as the opening theme (as well as Sign-2, an alternate version of Sign that was used as the game's end theme); both tracks were released by Hirasawa's Chaos Union company in downloadable format through Hirasawa's WORLD CELL MP3 ONLINE SHOP for 4 US Dollars on December 20, 2004.