Story pretty much translates to - The heroine's family has a proud history of police service, so she joined the service to honour her father's memory (it's implied he died on duty). There's a scene where she sees a robot girl in the train station and thinks nothing can beat a human touch.
Then she's hit by a truck and turned into a cyborg (her brain's in an android body) - her twin is a full-on android (with no human brain). Basically she's been convinced by the mad scientist she can still serve the public interest (and possibly rejoin the police force) with her new body. (see - nothing beats the human touch above)
The rest of it is pretty much typical craziness from the mangaka.