shakugan no shana
Shakugan no Shana (灼眼のシャナ, lit. "Shana of the Burning Eyes") is a 2002-2011 light novel series written by Takahashi Yashichiro and illustrated by Ito Noizi, with an ongoing 2005 manga adaptation illustrated by Sasakura Ayato and a three-season anime adaptation by J.C. Staff in 2005, 2007 and 2011.
Sakai Yuuji's ordinary life changes forever when he witnesses time stopping around him and a monster being slain by Shana, a red-haired petite swordsman, who proclaims that he is dead all along and is but a mere "Torch" - a specter of his former self bound to vanish any time soon. Yet through a mysterious power Yuuji is able to retain his existence, and thus he joins Shana and her faction, the Flame Hazes, in their long-standing struggle against the Denizens of the Crimson Realm, who are intent to use his powers to disrupt the balance of the world.