Grace, born Cynthia Landlavizar, is a 10-year-old prodigy who developed dissociative identity disorder as a defense mechanism against exploitation for her intellect. Her alternate persona, Grace, manifests as a sharp-tongued, headstrong counterpart to Cynthia’s silent, childlike vulnerability. The two identities share a fractured consciousness, alternating control while maintaining internal communication—a coexistence that drains Grace physically, worsened by her relentless work ethic.

As head of the Computer Security Department, Grace spearheads operations for MEMOL, the mansion’s governing supercomputer. Her prowess is tested during a cyberattack, where she thwarts external breaches with tactical precision. To shield Cynthia’s fragile mind, Grace once concealed her presence by adopting Cynthia’s identity during an amusement park outing, blurring their boundaries temporarily.

The "Blue Silent Bell" arc unveils Grace’s engineered origins, tying her existence to clandestine genetic experiments within the mansion. This narrative delves into the psychological toll of her duality, leading to interventions aimed at stabilizing her fractured psyche. A pivotal moment arises when Taro’s calming embrace during a panic attack soothes her distress, marking their deepening bond.

Explorations of an underground castle beneath the mansion later expose a portrait echoing another figure, hinting at Grace’s entanglement with the estate’s hidden history. Her technical mastery remains vital to safeguarding its digital infrastructure, often intersecting with crises involving rogue technology and internal power struggles.

Over time, Grace’s relationship with Cynthia shifts subtly—from a protective barrier toward tentative integration. Though her sarcastic wit and meta-commentaries inject humor, her arc persistently navigates resilience and the struggle to reconcile splintered selves amid unrelenting demands.