Kuriba Ryouko (Doppelganger)

A doppelganger (ドッペルゲンガー) of Kuriba Ryouko (操歯涼子 (くりばりょうこ)), said to possess a soul that was created during an experiment where the original Kuriba Ryouko was split into two cyborgs for a year before being recombined. Residing within the combined mechanical components and initially believing she was the real one, the doppelganger eventually realized what she was and escaped the laboratory to seek her original out.

Appearance
The doppelganger's face is mostly identical to the original Kuriba Ryouko, with vertically striped hair, alternating between light and dark from a dark stripe at the middle of her frontal fringe. There is a slight shade difference across her face, likely acquired during separation. Below her neck, her body's mechanical nature is more apparent with exposed joints and a set of panels opening onto a hole on her back.

Following her escape, the doppelganger acquired a black and pink patient gown and artificial skin to cover up her mechanical parts.

After the doppelganger assimilated an enormous amount of material after her container was breached, her appearance changed slightly, acquiring the darker skin over the entire body and completely white hair, as well as a dress made from pale threads.

Personality
It isn't yet known how much of the original Kuriba Ryouko's personality is shared by the doppelganger. After learning her true nature, the doppelganger displays a tendency for speculative talk regarding her nature as a fake compared to normal people, the body and the soul, particularly when harming others. She also shows no compunctions about severely harming anyone in her way or causing massive destruction in pursuit of her goals. The doppelganger stated that she wished to eliminate all threats to her existence and sought to kill her creator.

With the matter of the doppelganger's soul in doubt, Misaka Mikoto theorized that her despair might not just be from realizing she wasn't human, but from confirming that she didn't have a soul. The doppelganger later confirmed that her plan was to destroy herself along with any data and means which could recreate her, intending to trigger Academy City's defense systems to shoot her and the data storage airship down, seeing as she couldn't commit suicide herself. After Mikoto reluctantly fulfilled her wishes, she thanked her and described her destruction as being the same as throwing out a broken appliance.

Background
In the past, Kuriba Ryouko was involved in an experiment in which her body was split in two and the missing parts replaced with machines to create two separate cyborgs. After a year living apart, the two Ryoukos were recombined into one, with no split personalities or rejection, and retaining the memories of the time split apart. While Ryouko wished to test the compatibility between the cyborg technology and the human body, the institution she was working with also hoped to observe a possible side-effect - the creation of a "soul". Their hopes were supposedly realized with a new soul apparently being created and coming to reside in the cyborg parts which were assembled into a complete mechanical body. The doppelganger believed and perceived herself to be the original Kuriba Ryouko, unaware of her nature at first.

Dream Ranker Arc
Following the experiment, the doppelganger remained in the lab, supposedly to monitor after-effects, still believing herself to be the original human Kuriba Ryouko. Eventually she noticed gaps in her memory and realized what she was. She then proceeded to wreck the lab and escape by jumping out of the building, bypassing the precautions the scientists had set up on the lower floors. While falling, she passed Misaka Mikoto, who was following Kuriba Ryouko's trail. Mikoto attempted to break her fall with a banner, only to be caught out by the doppelganger's weight. The doppelganger escaped before Mikoto could reach it.

After her escape, the doppelganger visited the dilapidated Shinasame University DNA Map Analysis Laboratory, dealing with a group of thugs before acquiring some artificial skin to disguise her mechanical parts. She then accessed a pharmaceutical database and tracked down her original through her Miahilin prescription.

The doppelganger briefly cornered the original Ryouko, but she managed to escape using a countermeasure she had prepared. The doppelganger was then attacked by Scavenger, who had been sent by the lab to capture her. Following a brief skirmish, the doppelganger was restrained by Naru's telekinetically-controlled paper. However after Scavenger's leader taunted her for trying to be human, the doppelganger broke through the paper, grabbed her arm before snapping her bones, holding even while being hit by Naru's enhanced punches. She then moved to pluck out the leader's eye, but before she could, her head was smashed open by Naru's desperate attack.

Believing that the doppelganger was defeated, Scavenger moved towards tending Leader, but were then surprised as the doppelganger sprang upright. Naru moved in to attack again in her paper armor but the doppelganger stopped her punch and seized control of her paper, ripping it away to form a replacement arm and cover her head wound. The doppelganger then remarked on how she'd only just made the skin. A little later, after leaving Naru defeated and naked on the ground, the doppelganger turned towards Leader and Yakumaru. In response, Yakumaru pretended to flee to lure the doppelganger after her, using her chemicals to form a wall to cover her escape. As the doppelganger moved to break it, Yakumaru snuck behind her and used freezing chemicals to bind her. She then attacked the doppelganger, but it was revealed to be a paper clone. As the real doppelganger reached for Yakumaru's head, Naru managed to stop her temporarily, giving Yakumaru a chance to set off an explosion and escape with the others. Having shielded herself with her arm, the doppelganger remarked that she'd intended to let them escape alive to inform the lab, but decided she needed to investigate further.

Abilities
The doppelganger's body is comprised of medical cyborg parts, heavier and sturdier than normal body parts. The cyborg parts include artificial muscles which expand and contract through chemical reactions, and suppressants to prevent rejection when in contact with physical bodies, some of the technologies having been developed by the original Kuriba Ryouko. Her body also has a number of safety mechanisms, designed to prevent it from performing actions which would inflict damage to herself beyond a certain level. She is capable of withstanding falls, such as from the top floors of a multi-story building, and hits enhanced through Telekinesis to a certain degree. She can also scale walls and easily snap a person's bones. During her battle with Scavenger, the doppelganger appeared to display discrepancies from her provided specifications.

Having being fused with the brain of the original Kuriba Ryouko, one talented in the cyborg research field, and having spent a year learning and nurturing her creative abilities, the doppelganger's capabilities in those areas exceed those of an ordinary AI. In addition, she has calculation speed and simulation capabilities far greater than that of a human.

'Soul Possession'
One potentially dangerous aspect of the doppelganger is the nature of her apparently artificial soul. According to the original Ryouko, the soul is merely being stored within the mechanical body rather than being linked to it in the same way as a normal person. If the body was destroyed, the abnormal free soul (自由な魂) would be released into its surroundings, possibly being able to possess other things or maybe even engulf the city.

While still intact during the battle with Scavenger, the doppelganger was shown to be capable of exerting an influence on objects within a close proximity, interfering with objects under the influence of her opponents' abilities. After the body was breached by Naru, the doppelganger seemingly displayed the ability of soul possession (魂の憑依) to a much greater degree, being capable of possessing and moving much larger objects over a greater distance. Initially seizing control of Naru's paper and using it to form a replacement arm, together with nearby rubble, the doppelganger absorbed the materials around it and eventually grew a gigantic puppet body higher than a multi-storey building. When the giant puppet was heavily damaged, the doppelganger broke the rubble down into many fake copies of herself, controlling them all simultaneously, and was soon afterwards able to connect herself to the data storage airship.

However these capabilities were later revealed to be the result of an enhancement that the doppelganger created using resources at the Shinasame University DNA Map Analysis Laboratory and the abilities she had developed from being fused with the original Ryouko; self-replicating artificial muscles, possessing traits similar to those of ant parasites and slime mold, controlling materials by embedding themselves at a microscope level, later confirmed by the doppelganger. They resemble items from her creator's research papers from before the experiment, but have a slightly different form. The doppelganger likely predicted the original's soul diffusion theory and considered that the similarity in effect would be a considerable deterrent.

Created from mixing a type of slime mold with the muscles of a large herbivore, with air, water and light, they reproduce at a high rate though they deteriorate after finishing growing and shrivel up in a few hours. The thread-like extensions from the doppelganger are capable of moving large amount of material and extending over long distances, though they can still be cut and incinerated. As well as using them to manipulate external objects and debris, the doppelganger was also capable of forming weapons such as a sword and a drill.

Though the seeming soul possession was a deception and doubt was cast on the idea that the doppelganger has an artificial soul, whether or not she really does has yet to be fully verified.

Quotes

 * "People's thoughts are found in the brain. Their life is found in the heart. Their emotions are found in their face. Then, if you drive the soul from the body, would there be any vacancy there?" (人の思考は脳に宿る, 命は心臓に宿る, 感情は顔に宿る. なら――身体から魂を追い出せば空きができると思うかい?)
 * "Continuing to exist like this is nothing more than suffering." (この姿で存在し続けることこそが苦痛なのだ)

Trivia

 * Prior to realizing what she was, the doppelganger perceived certain machines and related objects as more human equivalents, such as a cleaning robot as a maid and a repair kit as a first-aid kit.