A nun at a local church, she looks after Kurou whenever he drops by for food, due to his lack of finances, although any payment he receives in his work is automatically given to her. Kurou met Leica when he first moved to Arkham City and she sheltered him from the elements for a time. The two of them then struck up an easy friendship with Kurou returning from time to time to play with George, Colin and Alison, the three orphans that live in her care. While compassionate, Leica is also cunning and perceptive, able to deduce that Kurou is getting himself into dangerous situations.
Leica is typically a supporting character but becomes a protagonist in her own route where it is revealed that she was a test subject in the Moonchild Project, an experiment conducted by the future Anticross, Vespasianus, in order to create the C Priestess, a being that was capable of interfacing with and controlling Cthulhu. The test subjects were artificially enhanced in various ways, with Leica becoming a living weapon with compressed magical spells embedded in her body that could be deployed at will. Eventually she escaped and hid among the population of Arkham City, posing as a nun while fighting against the Black Lodge as the hero Metatron. At the end of her route, she is transported along with Demonbane through time and space, fighting against the Liber Legis before a final showdown with the black angel, Sandalphon, who consistently opposed her. After time and space reassert themselves, she is transported by Al back to Arkham City with her past as Metatron and her association with the Moonchild Project wiped clean. Abiding by Kurou's request, Al allows him to retain his memories of the previous timeline and he continues to pursue a relationship with Leica.
As Metatron, Leica tries to dissuade Kurou from confronting the Black Lodge and does not believe herself to be the hero of justice that Arkham's population view her as. She possesses a suit of white, angelic armour that protects her from damage and allows her to fly. The armour is also equipped with a voice scrambler that hides her true identity. Metatron can also manifest wrist-mounted blades and beam cannons on her forearms, and is also a proficient hand-to-hand fighter. As befits a henshin heroine, she also has a signature attack, the Slash Cross. Later in the story she acquires the Hunting Horror, a flying motorcycle created by Doctor West that incorporates pages of the Pnakotic Manuscripts, giving it some of the characteristics of a Deus Machina. The Hunting Horror can only be driven effectively by an individual that has been artificially enhanced, such as Metatron or Sandalphon.