Twilight Frontier, also known as "Tasogare Frontier" or "Tasfro" for short, is a widely popular doujin circle known for their quality doujin games of varying genres. The games developed by the circle are often derivative works of other widely-known games while few others were actually made in collaboration of other doujin circles, such as ZUN, the creator of the Touhou series, and 07th Expansion of the Higurashi no Naku Koro ni fame.