堀鐔 (Horitsuba), short for 私立堀鐔学園 (Shiritsu Horitsuba Gakuen), Horitsuba Private High School, is a series of Drama CDs released in the annex of the Shonen Magazine and Young Magazine since 2006. Before having an anime version, some mangas have "Drama CDs". In these, they might tell the story of the manga itself or secondary/independent stories. In Tsubasa ~RESERVoir CHRoNiCLE's case, it's different since there is no drama of the manga itself, but of the Horitsuba Gakuen (Horitsuba Private Institute), a sort of alternate universe to both Tsubasa ~RESERVoir CHRoNiCLE~ and xxxHOLiC (hence the name: Horitsuba, formed by parts of the phonetics of the series' names, HORIkku and TSUBAsa), where the characters of both series appear in the quiet and peaceful Horitsuba Private Institute.