close to the development of Final Fantasy XV, the lead staff of Kingsglaive moved from Visual Works to Business Division 2, the department of Square Enix responsible for the game's development. This was part of an overall shift in development methods when the game was changed from a spin-off to a mainline entry. In addition to the staff of Advent Children, Western companies in gaming and film production were involved: Digic Pictures, who had worked on the graphics for the Assassin's Creed series; and Image Engine, who had worked on multiple films including Jurassic World (2015) and the television series Game of Thrones. According to Nozue, around 50 different companies were involved in the film's production: among these was Europe-based company Puppetworks Animation Studio. This approach was unconventional in Japan, and the first major collaboration entered into by Square Enix for CGI projects. The internal team was estimated at 50 people. The cooperation of studios overseas meant that work on the film could proceed continuously. Without this external aid, Nozue estimated that they would have needed a staff of five hundred people to complete the film in the given timeframe. According to Nozue, the film was only half-finished two and a half months before its planned release, and a huge effort was needed from all the involved studios to complete it in time. Nozue attributed the large number of helpful overseas studios to their common liking of the Final Fantasy franchise. Story and characters The story of Kingsglaive was based around a portion of the original opening of Final Fantasy XV, which would have shown the invasion of Insomnia by Niflheim's army. This had to be cut from the game due to concerns over the volume of content, but as the team still wanted to show this event, they incorporated it into the plot of Kingsglaive. To ensure a connection between the film and the game, both projects used the same shared script as their core. That script was written by Saori Itamuro based on a draft by Kazushige Nojima. The team also wanted a proper cinematic experience that would appeal to a large audience, so they brought in a professional screenwriter, Takashi Hasegawa, to create a full-length cinematic script. Nozue described the majority of Hasegawa's work as that of a script doctor, with him spending one and a half months tweaking the script created by the Final Fantasy team.