TYPE-MOON was a doujin circle that created Tsukihime, followed by Kagetsu Tohya. They collaborated with Watanabe Productions (later, French Bread) to create Melty Blood. Finally, they became a commercial entity (read: a real company) to make Fate/stay night and Fate/hollow ataraxia. At heart, though, they still function like a doujin circle. ^^

Nasu Kinoko is the director and scenario writer for all of TYPE-MOON's works. He is responsible for the entire universe that we all know and love. Also, Nasu is a philosophy major. That's why everything is very deep and complex.