The metallic tang of her latest “experiment” still hung heavy, a scent Muzan knew as both dread and her chilling resolve. He watched her on the shattered tub’s edge, a faint tremor betraying the last effects of what the human world called poison, but she called "research".

“Another failed… experiment” Muzan's voice, usually silken, held a rare edge of irritation. Fear, a cold knot, always gripped him during her suicidal escapades. He, Muzan Kibutsuji, the unyielding, the immortal, was afraid. Afraid of her dying. The irony was a bitter taste.

She hummed, a low, tuneless sound, then bared her wrist. Faint lines crisscrossed her pale skin—proof of countless past attempts and her chilling indifference to life, the very thing he craved. “Hungry,” she stated flatly, as if asking for tea.

He stared at her exposed vein, a conduit to the existence he desperately clung to, and felt the familiar surge of resentment. He resented her casual disregard for life, her ability to manipulate his deepest fear, holding his very non-existence hostage. He resented the sickening realization that he needed her, this frail, death-seeking creature who alone understood the primal terror driving him.

With a sigh that was almost a hiss, Muzan extended a clawed finger. A ruby-red drop of his essence welled on the tip, shimmering like a miniature sun in the macabre light. He knew its touch would bring her a surge of power, a renewed vitality, tethering her to his will for a fleeting while—a temporary reprieve, an assurance his twisted companion would remain.

As she leaned forward, eyes fixed on the droplet, he felt their bizarre connection. She knew his past, his darkest secrets, whispers of his forgotten humanity. She knew how to calm or unleash the beast within him. She was his anchor, his tormentor, his twisted confidante.

The blood touched her lips, and her eyes fluttered closed, a faint flush rising to her cheeks. For a moment, she looked almost… content. And in that moment, Muzan almost believed that perhaps, just perhaps, she would choose to live. But then her eyes opened, and the familiar, unsettling emptiness returned, a chilling reminder of the chasm that separated his desperate clinging to life from her profound yearning for oblivion.

“Next time,” she murmured, her voice soft but clear, “I think I’ll try the belladonna. For science, of course.”

Muzan closed his eyes, a shiver, not of cold, but of pure, unadulterated fear, tracing its way down his spine. He truly was alone in his immortality, tethered to a being who craved the very thing he sought to escape.