What anime/manga is this?

This anime/manga has a protagonist that is in a rebellion. He is in a city where one part is like an Eden of safeness and cleanliness while his people live in a ghetto-ish sort of place.the protagonist is a very skilled at fighting. But when he infiltrates the place he gets captured and turned into a robot that cannot defy his master. Now he is forced to protect the city he was trying to bring down. I really want to see/read this again. Need some help remembering the title. (and if it is an anime or manga... ^^')