Strange Steel Fairy Rouran(2012)

Strange Steel Fairy Rouran is a Japanese anime series that follows Rouran, a mysterious girl with no memory of her identity or origins. When the occult society Shiromorishuua unleashes monsters on Tokyo, the peace-keeping organization ASY deploys a Gousen—a metal faery—to defend the city. Rouran emerges as a powerful force, transforming into an avenging angel whenever she senses the Gousen or Kyoushi, reanimated corpses that threaten the city. Plagued by questions about her existence and abilities, Rouran finds refuge in Tokyo Arcadia, a settlement for expatriates and dissidents, where Tetsuya becomes her protector. As supernatural battles intensify, Rouran must uncover the truth behind her transformation and her role in the conflict between human and occult forces.