Mei Sagara (嵯峨良 芽依/Sagara Mei) is one of the heroines of the Kono Naka ni Hitori, Imouto ga Iru! series.
Mei's appearance is quite different as compared to other characters. Sheh as pale brown hair tied in a braided pony tail with a blue flower hair clip at the end. She also wears a pair of glasses. She usually wears her school uniform but wears a loose button up cardigan instead of a blazer. She also wears a witches hat and cape on some episodes. She is also seen wearing a maid outfit where she works
Mei normally appears as a cheerful girl with a mischievous side. She enjoyed teasing Shougo greatly, even once went as far as dressing up in a maid outfit with cat ears on her head to greet him. She usually called him "Onii-chan" (though unlike other girls who surround Shougo, Mei's feeling for him seems purely platonic.)
However, underneath Mei was skeptical of Shougo as a person, and he only earned her respect after he had proven that Mei had been deceiving him.
Mei was an extraordinary intelligent girl, having able to solve university-grade math problem when she was still a child in the orphanage. Two years before the series started, she wrote a research paper under her adopted father's guidance, and earned enough money to buy back the café her mother once owned.
Mei was an orphans who was picked up by her current parents. Her adopted father was a professor at the University of Massachusetts, while her adopted mother owned the café and took care of her. A few years later, her adopted mother died of illness, and Mei moved to Massachusetts to live with her father.
A third-year silver-haired bespectacled girl who dresses as a witch. She runs the Lyrical Sister Café which she describes as "a dream-like café where anyone can become an older brother or older sister!" Prior to the story, her biological parents abandoned her as a toddler because of her mathematical intellect and she was adopted by a university professor. She lived with her adoptive mother who owned and ran the café until she died. Afterwards Mei lived with her father in Massachusetts until she earned enough money to buy back the café. She and Konoe have the same brand phone. It is later revealed that she knows the identity of Shogo's sister, but does not want to expose her to the Mikadono family because she is an illegitimate child. After Shogo promises to protect her, she responds that she will reveal his sister's identity if he proves that he can be a good older brother.