The scenario for "Episode I" was co-written by Takahashi and his wife Soraya Saga. To ensure development of the game remained focused, Takahashi consulted the entire staff on the script's direction before the main production began. Takahashi initially planned "Xenosaga" to span six games, with a narrative divided into three parts all featuring the dual figures of KOS-MOS and chaos. The character of KOS-MOS was created by Takahashi. While human characters created by Takahashi and Saga were typically shown as strong despite having fragile bodies, KOS-MOS was designed to be the opposite; an "unbreakable" person with a fragile spirit. The names of KOS-MOS and chaos were deliberate plays on the philosophical concepts of order and chaos in the universe, tying into elements of Zen incorporated into the world structure. The game made heavy use of Biblical mythology, a trait shared with later entries in the series. The game's subtitle is taken from the native title of "The Will to Power", a collection of notes by German philosopher Friedrich Nietzsche. The use of Nietzsche's works and concepts was a recurring element in the series; within the context of "Episode I", the subtitle directly reflects the game's characters and the strength of their will. The Federation's military structure was based on the United States Army with some elements from the Imperial Japanese Army mixed in. In addition to references to Nietzsche, Takahashi incorporated references to Richard Wagner such as the ship name "Woglinde" due to Wagner's historic association with Nietzsche. Most notably however, are references to the works of psychiatrist C. J. Jung, fundamental to understanding the game's more unique concepts such as Unus Mundus, the Collective Unconscious, up to Rubedo.