Mao is another geass user who has a contract with C.C. His geass allows him to read the minds of others, which puts him in an advantegous position over everybody. However, his geass is always active, and he hears others' thoughts whether he wants to or not. Because of that, he is slightly insane and hates other people. He reveals that he read minds within 500 meters.
He is a Chinese orphan who was adopted by C.C. and later given a contract 11 years prior to the start of the series. The only mind that he cannot read is CC's because of that, he sees her as human, and has an obsession with her. He is always wearing headphones that plays C.C.'s voice, saying comforting words.
He came to Japan just to bring C.C. back with him, and when she refuses, he shoots her, and says he will cut her apart and make her combat. However, his plans are foiled by Lelouch, who uses Mao's obsession against him. When C.C. kills Mao, all she says is "Wait for me in C's World." He is a lunatic that enjoys messing with people.