Maria Takayama

Maria is the supervising teacher of the Neighbors Club; she is a ten-year old nun. While not unintelligent, she is often rude and immature and refers to others as "Rotten mandarin." She develops a sibling-like relationship with Kodaka who regularly makes her packed lunches, and is affectionate with him. She is also gullible, which Yozora uses to her advantage.

(Source: Wikipedia, edited)