Tsurara

Twin ninja maids who serve Liz, much like the Maid Guy & Fubuki. Although both are 21 years of age, Shizuku is the more youthful of the two. She has a tendency to speak out of turn to others, getting her into trouble often. Tsurara is the mature twin, upholding very strict codes of secrecy, infiltration and discipline. However, her dour attitude and voice makes her seem much older, ruining her disguises.
Source: Wikipedia.