Lily Heineman captains the Third Unit of Dorothea, the agency regulating illegal fairy usage. Though not a Fairy Soldier and unable to summon fairies as weapons, she holds her leadership role based on her capabilities. She possesses light brown hair typically worn in a ponytail and blue eyes, consistently appearing in the standard Dorothea uniform.

Lily's subordinates portray her as a trusted commander, indicating competence despite lacking fairy-based combat abilities. She participates in routine Dorothea duties, including firearms training at the agency's Rodancia quarters. Lily also attends agency social functions, such as a welcoming party for new recruit Marlya Noel at a bar where members engaged in casual conversation and drinking.