An ordinary high school girl Hoshino Ai (Shimizu Yuki) was carried off by somebody on her way to home. Afterward, she awoke at the hideout of Joker which Black Maria-the incarnation of evil is commanding. Fortunately she could escape by her teacher Aoyama's (Kida Tsuyoshi) support. But she was operated for replicant. Escaping from joker's hunter, she took counsel with her friend Katagiri Yumi (Nakamura Shizuka). However Yumi was also replicant, and Yumi was brainwashed and swore loyalty to Joker. Yumi mercilessly attacked Ai who was confused about Yumi's change. And the new strongest enemy appeared. At final pinch, wearing powered suits that from Aoyama, she became masked girl and stood up to the enemies.