Lilith displays short black hair, a dusky tan complexion, and distinctive deep purple eyes. Her curvaceous figure is typically clad in a maid outfit featuring a revealing bodice. Notable features include two moles under her right eye and one on her chest.

Her personality blends diligent professionalism with playful teasing. She executes household chores with exceptional skill, rapidly mastering cooking and cleaning. While she frequently teases Yuuri, aiming to elicit flustered reactions, his blunt honesty often reverses the dynamic, leaving her embarrassed. Despite this, she demonstrates genuine care for him, evolving from professional duty to familial affection. Her sarcastic confessions to Yuuri's accusations commonly backfire when he interprets them literally, resulting in comedic yet heartfelt moments.

Orphaned early, Lilith faced rejection from multiple families who disapproved of her purple eyes. Yuuri's parents eventually offered permanent adoption. Though grateful, she declined to pursue maid training at a boarding school instead. After graduating, she worked elsewhere until learning of Yuuri's parents' death. She then left her position to care for Yuuri, driven by a desire to repay his family's past kindness and prevent him from experiencing the loneliness she endured.

Her relationship with Yuuri forms her core development. They first met when he was a toddler; he admired her eyes unlike others, though he later forgot this encounter. Upon reuniting, she concealed their shared history, fueling his initial suspicions. Her teasing gradually reveals deeper affection, particularly when Yuuri declares her part of his family or resists her potential departure. Key developments include her panic when Yuuri stops calling her suspicious, her distress upon receiving a recall letter from her former employer, and her vulnerability when falling ill—prompting Yuuri to reciprocate care. The narrative culminates with Yuuri recalling their childhood connection and confessing his love, while Lilith fully commits to staying as his protector and emotional anchor.

A recurring symbol is her purple eyes, initially hidden behind bangs due to childhood ridicule. Yuuri's childhood admiration and later portrait emphasizing them signify acceptance central to her emotional arc. Flashbacks reveal she sang lullabies to him as a child, a detail resurfaces when he recognizes her voice. Her background resolves through layered revelations: early hints in flashbacks show her reacting to his parents' death, while later episodes fully unveil her history with the family and decision to prioritize Yuuri's wellbeing over her career.