Riri Hamilton, daughter of a Scottish alchemist, was shaped by his experimental alchemical procedures that imbued her with psychic abilities to read minds and sense emotions. Though the experiments initially granted her mind-control capabilities, a fellow alchemist intervened to neutralize this power, leaving her solely with telepathic and empathic gifts.

Rescued from her father by the phantom thief Hyakushiki, she is taken under his wing as his ward, affectionately calling him "Uncle." She forges a steadfast bond with Dullahan, a headless robotic companion crafted by her father, who evolves into a protective figure within her newfound family.

Her journey involves striving to emulate Hyakushiki’s phantom thief persona, adopting facets of his identity while navigating ties to the Yoshinaga family and their guardian gargoyle. This mirrors her transition from a sheltered upbringing to forging her own path, though her ventures into thievery lean toward comedic misadventures rather than calculated crimes.

Her interactions underscore her gradual integration into a nurturing community, balancing extraordinary gifts with ordinary struggles. The lingering alchemical legacy of her past subtly shapes her deep empathy and connection with non-human entities, from sentient statues to artificial beings, threading through her evolving understanding of identity and belonging.