Lili Hamilton first appears as a friend to Futaba Yoshinaga. Her past involves enduring experimental alchemy at the hands of her father, Hamilton, a Scottish alchemist. These procedures granted her psychic powers, specifically the ability to read minds and sense emotions. Initially, these experiments included "Mind-Control Eyes," later healed by the alchemist Iyo Takahara.

Her life shifts dramatically when clever thief Kaito Hyakushiki rescues her from her father and becomes her guardian. She subsequently moves in with Hyakushiki, whom she affectionately dubs "Uncle." This bond forms a cornerstone of her growth, leading her to see Hyakushiki as family. She sometimes aids or mimics his gentleman thief persona, even temporarily assuming his role alongside the alchemical creation Dullahan during his illness.

Lili becomes part of the Goshikichō community, joining local festivals and initiatives supporting the shopping district. Her psychic abilities frequently aid communication and mutual understanding between characters, with the narrative highlighting her non-malicious use of these powers after her healing.

Lili also features in the spin-off "Gargoyle Alternative," though no specific developments or expanded backstory within that series are detailed. Her core narrative arc remains focused on her found family dynamic with Hyakushiki, her friendships, and her adaptation to freedom from her father's experiments.