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 known how much of the original Kuriba Ryouko's personality is shared by the doppelganger. After learning her true nature, the doppelganger displayed 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 showed 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.

Much like her original, the doppelganger accepted sacrifice as a necessary condition to achieve something, that being the reason she tried to terminate her original rather than a grudge.

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.

As the doppelganger continued to move through an industrial area, towards the data storage airship containing the experiment's data, she was confronted by Misaka Mikoto, accompanied by Leader. Overcoming Mikoto's attempt to trap her and retaliating by throwing a gas tank, the doppelganger told her that it was too soon for them to fight, before building up a large puppet body from rubble, prompting Mikoto to remark on the similarities to another foe she had fought before. As the doppelganger continued to move, she and her large puppet ended up going through a building where one of the project researchers was waiting for Scavenger to deliver her.

With Mikoto continuing to impede her, the doppelganger absorbed a huge amount of rubble and enlarged her puppet to gigantic proportions. As Mikoto damaged the puppet, the doppelganger continually repaired it. Mikoto responded by creating her own giant puppet from iron sand, eventually using it to breach the doppelganger's puppet with an enhanced railgun shot and sent iron sand into the wound to cut the threads binding the puppet together.

After her giant puppet was destroyed, the doppelganger broke the rubble down into many fake copies of herself before using threads extending from the copies and herself to reach the airship. As the original Kuriba Ryouko arrived and told her that she wished to talk, the doppelganger brought her and herself onto the airship. Hearing about her original's Indian Poker and her offer to erase her own soul so the doppelganger would have a human body, the doppelganger replied that she had no interested in her body and just wanted her dead. She was somewhat surprised when Ryouko, stating that her own life was of no consequence now that her mother's survival was assured, let go of the airship and let herself fall, before Scavenger intervened.

As Mikoto climbed onto the airship, she and the others deduced the true nature of the doppelganger's 'soul possession' and the cause of the doppelganger's despair. After describing the slime-mold mix and her apparent plot to drop gas tanks onto the city, the doppelganger resumed her battle with Mikoto. When Mikoto intentionally missed a fatal shot with her railgun, the doppelganger asked why she missed, leading Mikoto to realize she was right about what the doppelganger's true intentions were. Mikoto asked the doppelganger if she couldn't live as she was, which the doppelganger described as a cruel request. Describing how continuing to live in this fashion would be nothing but suffering, the doppelganger asked Mikoto to end it. Mikoto reluctantly complied, bringing down the doppelganger and the airship with a thundercloud.

Heavily damaged, the doppelganger thanked Mikoto for fulfilling her wish. Seeing Mikoto's unhappiness at having to perform this action, the doppelganger remarked on her soft-heartedness, compared the action of destroying her as being the same as throwing out a broken appliance. She confirmed Mikoto's theory that she trying to trigger Academy City's defense systems to shoot her and the airship down as she couldn't commit suicide herself. The doppelganger then witnessed the arrival of her original and a brief confrontation with the project's head researcher which resulted in Ryouko getting shot. As Mikoto tried to help Ryouko, the doppelganger remarked on her original's luck at having suitable cyborg replacements nearby before ceasing to function.

Parts from the doppelganger were successfully used to save Ryouko's life. Afterwards, she began to see the doppelganger in her dreams. Initially she thought it was a hallucination brought on by her guilt, but the doppelganger in her dream had an accurate record of her battle with Mikoto, something which Ryouko herself didn't know. When Ryouko asked if this was a chance for her to apologize, the doppelganger told her that she wasn't trying to kill her over a grudge but as a necessary condition, noting that accepting that sacrifice as such may have been an influence created from Ryouko's thought patterns, describing how Ryouko spread Indian Poker despite knowing it would cause chaos in order to save her mother and didn't make an exception with regards to her own life. While noting that Ryouko was a person who couldn't accomplish anything without sacrifice, the doppelganger told her that there was no need to reject who she was, as she would become someone who would harm nothing but also create nothing, which would make sharing her life boring. Since then, the doppelganger kept appearing in her original's dreams and pointing out points for correction in her research.

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. After the original Kuriba Ryouko was saved through a transplant using some of the terminated doppelganger's parts, the doppelganger appeared in her dreams. Initially thought to be a hallucination brought on by guilt, the dream doppelganger possessed the calculation abilities and the memory that the doppelganger would have, including an accurate record of her battle with Mikoto, something which Ryouko didn't know.

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.