The game's story was written by Sakaguchi, whose main aim was to create a highly emotional experience that explored the human psyche. According to him, the game's setting revolved around conflict and its effects. In addition to Sakaguchi's work, Japanese novelist Kiyoshi Shigematsu created over thirty stories detailing Kaim's life as an immortal, titled "A Thousand Years of Dreams". According to Shigematsu, it was the first time he had ever worked on a video game, and was unsure about whether he could evoke emotion as he did in his books. In the end, he found that the interactive medium gave his work a new impact that moved him to tears upon seeing it in place. These story segments were presented in the game in a similar style to a visual novel, as the stories were intended to evoke emotion. The gameplay, such as the battle system, was kept deliberately traditional so that Sakaguchi had freedom to experiment with the story. Despite this, he wanted to introduce new real-time elements into the system. One of the elements Sakaguchi checked was how story and gameplay were balanced: sometimes, he would ask for a cutscene to be removed or for a boss battle to be lengthened if the balance seemed off.