Iron Maiden -Hagane no Otome-

When the main character is relaxing in his room, a blackout suddenyl occurs. He is wrapped by something strange, and it seems like someone coming closer in the dark. A girl suddenly appears in front of him. She looks like an ordinary girl but she wears something machine-like cloth. When he wakes up, there is no girl anymore... Next morning, he remembers what happened last night. "Was that just a dream?" When he goes to school, he is surprised to see girls wearing the machine-like clothes like the one he saw yesterday...