Lieutenant Mizuki was the first to be transformed into the "ultimate weapon" before Chise took on the mantle. Despite being a hardened military veteran, Mizuki's injuries impeded her ability to fight, and she willingly participated in an experimental procedure. As the prototype for ultimate weapons, Mizuki proved to be a formidable force on the battlefield, but her development was restricted as the initial candidate. Subsequently, the emergence of Chise, a more suitable candidate, led to Mizuki questioning her aptitude. Mizuki dismissed Chise's competency as she believed she was fragile and foolish, unlike herself. However, being the only one to have gone through the transformation before Chise, Mizuki could hear her thoughts, which made her the only one who could relate to her. Meanwhile, as the ongoing war progressed, and Chise evolved, Mizuki learned more about the intricacies of ultimate weapons, Chise, and herself.