Mary Sue

Mary Sioux a.k.a Mary is one of the main antagonist of the series, the ultimate rival and the tool used by Being X inorder to stabilize a neutral war against Tanya Degurechaff. She is the sole daughter of Anson Sioux.

Her real name is Mary Sue, which makes "Sioux" mistranslation.

Appearance
Mary is a young girl with brown hair and brown eyes. When she was still an ordinary citizen, she was seen wearing a blouse with long skirt. As a volunteered soldier, she is seen wearing an US military uniform.

Trivia

 * Her name "Mary" comes from the biblical character named "Mary of Nazareth".