XD Hey welcome to anime. Usually Anime production committees are composed by the Manga (or Light Novels) Publisher, the Animation Studio and a Music Label plus other related companies (video games , toy sellers etc.). Since anime there are as mainstream as any pop cultural gimmick, is an ease way to sell music, introduce new bands, get promotion etc.. so you may find really over the top quality music in some openings and endings. Guilty Crown have mixed reviews, good animation, not so good story, excellent music. Is well know because, My Dearest was composed by Supercell, a well know music composer you may find in others animes ops and eds if you continue into the rabbit hole. XD