Nemesis

Nemesis (ネメシス, Nemeshisu), also known as Master Nemesis, is a character introduced in To Love-Ru: Darkness. She is a transformation weapon, much like Golden Darkness (Yami) and Mea Kurosaki, but does not share their genetic origins. She is Mea's master, whom she gives orders and uses to observe Yami's changes and recent life. At the beginning of To Love-Ru Darkness, her original plan was to make Yami return to being the heartless assassin she was before arriving on Earth and she convinced Mea that this was the only life they were meant to live as weapons. Due to her catalyst-like role in the overall plot, she is considered the central antagonist of To Love-Ru Darkness.

Because she wants Yami to join her and become an assassin again and wants Rito for herself (as her servant) because of his ability to influence Yami and Mea, Nemesis is essentially also the direct opponent to Momo's plan to include Yami, various other girls and herself into a harem for Rito. As of Chapter 61, after a long and arduous battle with Gid Lucione Deviluke that left her on the brink of death, she accepted Rito's offer to "possess" and live in his body until she is able to recover fully, given her the ability to control his speech and body movements for small amounts of time.

Her real name is unknown and the name 'Nemesis' is based from Project Nemesis, a weapon project that was organized by the assassin organization that created both Yami and Mea. However, this project, as stated by Tearju Lunatique, was a failure, but Nemesis survived the project.

Appearance
Nemesis is a petite-looking girl with long black hair, golden eyes with vertical silt pupils and tanned-skin. Based on her physical appearance, Rito had mistaken her as a little girl. However, she can change her appearance into anything she desires, such as a crow or a cat, or change her herself into a well-endowed adult woman (as a benefit of having complete hormonal control of her body). She has taken to giving herself cat ears often.

At first she wore a scanty black dress, but she used her abilities to change it into a black yukata (claiming how effective it is in a fight) with a star shaped gap symbol on it (similar to the one Yami and Mea have on the chest of their black gothic clothing) and she has a yellow sash wrapped around her waist. When she changed to black yukata first time she had a cat mask which combine with taichi figure covered left side of her head as decoration.

Personality
Nemesis is sadistic, mischievous, domineering and mysterious. She believes that a transformation weapon's only purpose for living is killing. She is often seen hiding in the shadows observing Rito, his friends, and their daily lives through Mea, until she began to approach them herself. She also has an eery and erotic side to her and finds Rito's shyness arousing and would like to have him as her servant. She said that she doesn't have full control over her erotic personality and would act on it on impulse. Upon her first appearance, her erotic tendencies quickly earned an uneasy impression from Rito and a strong disdain from Momo. She can be quite patient, like instead of persuading Yami to return to her old heartless life, she decides to wait until she uses the "Darkness ability", believing that Yami will return to that path naturally and that the "Darkness" will inevitably occur regardless of Yami's relationships on Earth.

Like Mea, she has a sweet tooth; she enjoys eating anything that contains Dark Matter.

She is eerily optimistic and apathetic at all times, and whether things go her way or not, when she is not entertained, she does little to show any negative feelings for any reason. Even after Mea disobeys her and her plan to activate Yami's Darkness transformation failed, she does not appear to mind. And even after a fierce battle left her on the verge of imminent death, she expresses no regrets disappearing after all of the fun and mischief she had, as well as some relief towards the thought of her life coming to an end, indicating that beneath her childlike and bratty demeanor, she's a truly depressed and lonely being.

It is unknown if Nemesis has feelings for Rito, but she enjoys being fused with him, as she teases him when the opportunity presents itself and comments that her life is now more interesting now that she is fused with Rito.

History
Nemesis was the result of "Project Nemesis", a different experiment from the project that created Golden Darkness, conducted by the organization known as Eden. The experiment was an attempt to create a living weapon composed of Dark Matter, which was abundant throughout the universe. However, the project was scrapped and abandoned because of the scientists' failure to materialized form. But unknown to them, Nemesis existed as a formless and unseen intelligence, wandering the facilities for years and overseeing the creations of Golden Darkness and Mea, both human-based Transformation weapons, until the organization's collapse at the hands of Black, and Mea's release.

Mea remembers that Nemesis came to the fallen organization where she found Mea and decided to raise her. At that time, both their physical condition were unstable and Nemesis was on the verge of disappearing, so she used her ability to fuse with Mea to stabilize herself. Nemesis always created images of herself to make Mea believe that they are both speaking to each other as separate people, and Mea was unaware that Nemesis existed inside her body.

Nemesis taught Mea that the purpose of a Transformation Weapon is to kill. She also taught her about her sister, Golden Darkness, whom they came to Earth to bring back into space as who she was before.

Powers and Abilities
Dark Matter-based Physiology: Nemesis' body consists of dark matter that allows her the trans ability rather than having nanomachines. While she possesses the same common shape-shifting abilities as Yami and Mea, her powers are fundamentally different in nature and possesses some abilities unique to herself.
 * Shape-shifting: Nemesis can alter her appearance and reshape her body to look more adult-like and even change her appearance to look exactly like other people. She can fully transform into animals, even those much smaller than herself, such as a crow or a cat. She can also grow a pair of butterfly wings that gives her the ability to fly.
 * Attire Transformation: She is able to transform her clothing, as seen when she switches between a black nightgown and a yukata. She is also seen wearing a maid outfit.
 * Hair Manipulation: Nemesis is capable of controlling the movement of her hair, altering it's length and transform it into any animate object such as weapons.
 * Vocal Alteration: In addition to her shape shifting abilities, she can also change her voice to sound just like anyone.
 * Trans-Fusion: One of Nemesis' own unique abilities, which allows her to fuse her body with that of another person. She was forced to fuse herself with the body of Mea Kurosaki, where she continued to watch things happen around Mea from inside her body. Nemesis explained that she used this ability on Mea because at the time, Nemesis was in a physically unstable condition, and so she needed to exist inside Mea's body as a vessel until she can stabilize herself, and then she can leave Mea's body. While under Trans-fusion, she is able to communicate with Mea, and even create an image of herself in her mind, so as to give Mea the illusion of them speaking with each other face to face in the physical world. This ability is not limited to another Tranformation Weapon, as she is able to fuse with Rito, which gives her the ability to forcefully control his movements for a short amount of time, depending on her current strength. For manipulating other people's body, Nemesis uses a voodoo doll
 * Weapon Transformation: Nemesis is capable of transforming her body into different forms of tools and weaponry of various sizes, most notably blades.
 * Partial Materialization: An ability that Nemesis uses to materialize the scattered dark matter from her body to form hands and weapons from any spacial range without being attached to her body. This can also be used to reconstruct her body to reappear in any location.
 * Regeneration: Her body is nearly immune to physical and light energy attacks since they'll phase right through her, as she can reconstruct herself from any damage taken, however her body won't be able to keep up if taken too much damage.
 * Body Jack: She is able to hijack the bodies of several lesser-minded individuals even if they were conscious beforehand. While under such effects, her victims have the appearance of zombies and borrow a fraction of her strength in order to hold their own in battle. It is also shown that she is able to speak through them, as she speaks through Saruyama in order to communicate with Yami.

Trivia

 * Nemesis' name comes from the Greek goddess of indignation against, and retribution for, evil deeds and undeserved good fortune, Nemesis.
 * Her measurements are B65-W51-H68.
 * According to the modern physics, Dark Matter cannot be seen by naked eye. However, in To Love-Ru Darkness, Dark Matter can be seen with black color.