Total Human Cyborg Replacement Project

The Doppelganger Experiment (actual name unknown) was a cyborg experiment carried out in Academy City.

Background
The experiment was devised at a certain institution in Academy City, which had initially had trouble finding volunteers, given its unprecedented nature. Kuriba Ryouko, who was working at the institution in order to develop a cyborg treatment for her mother, ended up volunteering for the experiment to gather the necessary data in the short time she had left. Her body was subsequently split in two and the missing parts replaced with machines to create two separate cyborgs. Acting as both observer and specimen, she planned to use the experiment to gather data on every part of the body. After a year living apart, the two were recombined into one, with no split personalities or rejection, and retaining the memories of the time split apart.