Artist's comments: -- I drew my impression of Suzume. These are the battle form 1, the full-size battle form, and the uniform version. She's a 13 year old first year middle school student like Kyousuke's little sister Hina. Hiyama Suzume. She's got a flat chest, yep. lol Obviously, the human form is just an assumed form for living in the human world, and when worse comes to worst she transforms into a mechanical giant. She can change her size freely from human size to that of a high-rise building. However, since she had some power sealed away by Kyousuke, she cannot transform without Kyousuke's permission. --
Next time try to track it down yourself, though. Now, if someone could find out what game or series she is from...