Leyla M. Ruzhkova, a human-demon hybrid called a Nadezhda, emerged from a covert Moscow project designed to bridge human-demon coexistence. Scientist Natalia Ruzhkova acted as both creator and surrogate mother, raising Leyla and her younger sister Klara despite Leyla's hidden shame toward her demonic traits. Her appearance features silver hair and blue eyes, typically adorned in a patterned navy blue mini dress, black gloves, pantyhose, a thigh belt, and heels. In her Nadezhda form, she manifests black angelic wings, a revealing black outfit, red claws, and crimson tattoo-like markings across her face, stomach, and legs. Her eyes shift to red-glowing diamonds while sharp teeth emerge. Initially, she concealed this form beneath a black robe and metal helmet while infiltrating the New Moscow Combat Revue.

Stoic and fiercely loyal, Leyla devoted herself to Valery Kaminski after he alone called her beautiful and powerful despite her hybrid nature. This loyalty drove her to aid his quest to destroy and reshape the world, even after uncovering his true motives. She helped dismantle the original Moscow Combat Revue and joined his imposter Revue to reclaim Klara, all while wrestling with jealousy over Klara "stealing" Kaminski's attention—a conflict between her allegiance to him and love for her sister.

Her core drive to reunite with Klara propelled her to battle White Cape, Lancelot, and Elise atop a Russian train. Cornered, she escaped by plunging off the train and taking flight. Later in Tokyo, she aggressively pursued Klara at the Imperial Theater, ignoring her sister's terror and nearly injuring Hatsuho Shinonome during an intervention. Alongside Kaminski's forces, she effortlessly defeated a demon while mocking the Flower Division's combat skills.

As events unfolded, Leyla witnessed Kaminski manipulating Klara through Black Cape's trauma. Though voicing unwavering loyalty, Klara's suffering visibly troubled her. Aboard the Sevastopol airship, she fought the Flower Division during Kaminski's repairs to the Tunguska Cannon. Witnessing Klara's anguish finally shattered Kaminski's hold: Leyla freed her sister but sustained mortal wounds. With her last breath, she urged Klara to stay with the Flower Division for safety and happiness, sacrificing herself for her sister's escape.

After her apparent death, an ambiguous figure resembling Leyla appeared in Shadow Tokyo, observing a dissipating crystal—leaving her ultimate fate unresolved.