Ehavilla Mecco possesses striking blue eyes and long blue hair reaching her hips, featuring a braid, blunt bangs, and a hair ribbon. She consistently presents a professional, scientific image, commonly seen wearing glasses, a labcoat, a red shirt, a suit jacket, a necktie, and formal attire. As a human scientist within WIME's Army, Ehavilla exploits her position to pursue a personal agenda starkly opposed to the organization's matriarchal goals. She is driven to achieve the complete eradication of males, focusing her efforts on genetic research to biologically alter women, rendering male involvement in reproduction obsolete. Her work involves direct experimentation on test subjects, including the escapee Yume, whom Ehavilla is persistently hunting down to reclaim. To enforce her will, she employs advanced mental manipulation and mind control techniques, demonstrating exceptional skill in dominating and breaking the wills of subordinates, a capability noted as comparable to other specialists within the series. Ehavilla operates without ethical constraints, embodying a purely utilitarian philosophy where any action is justified to reach her objective of male extinction. She is calculating, manipulative, and relentlessly focused, showing no trace of moral hesitation.