Kikou Sennyo Rouran

Strange Steel Fairy Rouran (奇鋼仙女ロウラン, Kikou Sennyo Rouran) is a Japanese anime that aired on Kids Station in Japan from November 15, 2002 to May 30, 2003.

Plot
When the secret occult society, Shiromorishuua, sends a huge monster to attack Tokyo; Japan's peace-keeping organization, ASY sends its Gousen (metal faery) to destroy the creature but soon to be ambushed afterwards. But an unknown girl named "Rouran", who can float in midair with glowing radiance, strikes with a beam of light. Rouran has no clue of her identity, origins, nor why whenever she senses the Gousen or Kyoushi (reanimated corpses) she transforms into an avenging angel. As Rouran worries about her mysterious existence, Tetsuya kindly watches over her in Tokyo Arcadia, a settlement of expatriates and dissidents.