Saint Marie

Dah-In Hyun, a normal everyday schoolgirl, discovers that she and the other students at Saint Marie have become pawns in a proverbial chess game. When her best friend dies trying to defend herself, Dah-In finds herself trapped in a battle where no one is who they seem, and the line between black and white is blurred. (Source: Wikipedia)

Saint Marie had two volumes published in English by ADV Manga from May 25, 2004 to September 21, 2004 before the license was dropped and the publisher went defunct.