Jeanne Saya emerges as a descendant of Joan of Arc, recruited by the Khronos Foundation. She joins other heirs to legendary figures like Musashi Miyamoto and Napoleon Bonaparte in a desperate struggle against an invading extraterrestrial force known as Obliquus. To confront this threat, Jeanne undergoes fusion with biomechanical battle suits called Gears, transforming her into a specialized biological weapon designated a Khronos Gear. This transformation is a critical part of the Foundation's initiative to create enhanced human warriors. Jeanne resides and trains at the specialized school campus established by the Foundation to prepare the Khronos Gears for combat operations.