Lan-Mao is a young woman of Chinese descent who serves as the personal assassin and bodyguard for the opium dealer Lau. She has a striking appearance with large golden eyes and long, jet-black hair styled in thin braids and twin buns that resemble cat ears, often adorned with a flower ornament and a tassel. She typically wears a short, blue-trimmed lavender Chinese dress. Lan-Mao is a reserved and largely silent character who rarely speaks more than a few words and maintains a consistently expressionless demeanor. Her motivations are simple and unwavering: she follows Lau without question, acting as his instrument in violent affairs and eliminating those he considers enemies. Lau introduces her as his little sister, though they are not related by blood, and their bond appears to have existed since childhood. In the story, Lan-Mao acts as a secondary antagonist and occasional ally to the Phantomhive household, appearing alongside Lau during various arcs such as the Indian Butler competition and the murder mystery aboard the luxury liner. Although she seldom shows emotion, she is deeply loyal to Lau and is capable of great violence when directed, wielding two large, heavy ornamental clubs or spiked mallets in combat. Her strength is notable for her size, with Sebastian once remarking on the destructive power contained within her small frame. Over the course of the series, she remains a relatively static character, though later storylines hint at a growing closeness with other servants such as Mey-Rin. Her combat prowess and unwavering loyalty make her a formidable presence whenever she acts on Lau's behalf.