High Quality Content by WIKIPEDIA articles! The fictional characters appearing in the manga and anime series xxxHolic were developed by Clamp, a group of four manga artists. Taking place in a modern Japan, the series focuses on various supernatural themes, leading to various of the characters being spirits or mysterious creatures. Published at the same time of Clamp`s Tsubasa: Reservoir Chronicle manga, xxxHolic often makes crossovers with it, leading to the appearances of various of its characters in the series.