Teitania da Montewells is a Nextant, a genetically engineered human successor to the Perfect Soldier program. Designed for combat, she serves as both a pilot and a living component integrated within advanced mecha systems. She operates under the command of Viachevlav da Montewells, a cardinal of the Church of Marteal, with her deployment focused on influencing papal succession. Her primary target is Chirico Cuvie, designated "The Untouchable" due to his religious significance.

Her initial missions require converting Chirico to the church's doctrines or eliminating him. During a direct combat confrontation, Chirico shoots her, causing injuries. This event triggers an unforeseen reversal in her allegiance and emotional state, igniting intense romantic feelings towards Chirico despite their adversarial roles. This emotional shift compels her to defect from the church's forces.

Following her defection, Teitania aligns herself with Chirico. Her actions contribute to destabilizing the papal succession process and altering political dynamics within the Church of Marteal. Her narrative arc concludes as she departs the church's hierarchy, accompanying Chirico away from the central conflict zone.

Her combat role exemplifies the fusion of biological and mechanical systems, functioning as the human counterpart to Armored Troopers. This integration signifies an evolution beyond earlier Perfect Soldier prototypes.