Here are all the characters from the first Volume of the X manga. I'm just guessing at the hair colors, so they're probably wrong. Also, these are only the people with names.
Arashi- The black haired girl who saves Saiki from Kamui. She can pull a sword from her palm.
Hien- The brown haired priestess of Princess Hinoto. She helps take care of Hinoto.
Monou Fuma- He looks stern but is really very kind. He and his sister, Kotori, were raised by their father after their mother's death. He is a junior at the same school as Kotori. He is very unemotional.
Monou Kotori- She is the childhood friend of Kamui, and classmate. She and her brother, Fuma, were raised by their father after her mother died. She has a weak heart like her mother. She is well-like and a sophomore in high school. She lives with her brother and father at the Togakushi Shrine in Tokyo.
Princess Hinoto- She is the prophet of Japan's future who lives beneath the Diet Building. She cannot sea, speak, hear, or walk. She used her foresight to see Kamui's arrival and the end of the world. She is a blind diviner, fortune teller, prophet, and dreamseer. She dreams for politicians.
Saiki- The blond stranger who first fights Kamui outside his old house. His element is air.
Shiro Kamui- He left Tokyo six years ago with his mother. He is a sophomore at Kotori and Fuma's school, and in the same class as Kotori. He doesn't care if he hurts others or destroys property in his fights. He was friends with Kotori and Fuma when he was younger.
Sohi- The white haired priestess who takes care of Princess Hinoto.