text: Development Kinoko Nasu first began writing Fate/stay night in college and had not intended it to be a game. Initially, Nasu only wrote what would become the game's Fate storyline. However, the game went on to have three storylines, the Fate storyline being one of them. In his early drafts, Fates heroine Saber was a man, and the protagonist was a girl with glasses. This early draft was later embodied in the short original video animation (OVA) Fate/Prototype, which was released with the final volume of the Carnival Phantasm OVA series. Nasu set aside the project and went on to found Type-Moon with artist Takashi Takeuchi. After the success of their first visual novel Tsukihime in 2000, Type-Moon transitioned from a dōjin soft organization to a commercial organization. Nasu and Takeuchi decided to turn the old Fate story into a visual novel as Type-Moon's first commercial product. In the beginning, Nasu was worried that because the main character was a girl, the story might not work as a bishōjo game. Artist Takeuchi suggested switching the protagonist's and Saber's genders to fit the game market.
  The novel Makai Tensho influenced Nasu to write a fantasy story in which famous heroic personalities from all over the world would take part. The original idea was limited to the prototype of the Fate arc, where the main characters were the female master and her Servant Saber (the embodiment of King Arthur as a man). According to Nasu, this version contained elements of 1980s romance and ideas of transformations to world order, while the final version focuses on changes within people and has other purposes for using the Holy Grail. About a third of the scenario of the future Fate arc (up to the battle with Sasaki Kojiro) was completed at that time, but for several personal reasons, Nasu could not write further for more than ten years.