Fuyuna Shinzaki, the protagonist’s cousin, shares a home and school with their family. A studious honors student with a quiet, reserved nature, she deflects praise for her academic success with modest dismissals. Her jealousy festers silently as her cousin garners admiration for fortune-telling talents, while her own unspoken passions and hobbies remain stifled. Resentment simmers beneath polite interactions—avoiding conversations about her interests, tensing when others celebrate her cousin’s activities over her achievements.

This envy deepens as peers gravitate toward her cousin during school breaks, leaving Fuyuna increasingly isolated. Her despair draws a Daemonia, a creature feeding on anguish, which seizes control of her. The possession starts with withdrawn silence during meals and vacant stares, escalating into a grotesque metamorphosis that twists her body into a vine-strewn monstrosity. In this form, she confronts her cousin, attacking with strangling tendrils before being obliterated, her life severed in the clash.

After her death, all traces of Fuyuna vanish from family and societal memory, save the protagonist’s fractured recollections. A flower brooch she once gifted briefly lingers as a fleeting keepsake before dissolving. A journal emerges, its pages whispering unspoken regrets, only to fade like smoke. Her erasure haunts the protagonist, fueling doubt over the ethics of battling Daemonia—knowing each victory demands sacrificing the human host.