Zero

Zero was the elder sister of Kirinmaru and a major antagonist of Hanyō no Yashahime who informed her brother of the prophecy the Shikon Jewel had predicted, that he would meet his demise at the hands of beings that are neither human nor demon and an impossible entity surpassing time itself.

As such, she was bent on ensuring the demise of Sesshōmaru and Rin's half-demon twin daughters, and Inuyasha and Kagome Higurashi's only quarter-demon daughter to prevent the fulfillment of the Jewel's additional prophecy, although her ultimate goal and motivation for such a feat still remains a mystery as of now. In reality, she desires to make Towa, Setsuna and Moroha suffer and bring about utter misery. That was until the thread of fate connecting her to Tōga was severed, and she died after being stabbed by Riku.

History
600 years ago in the Heian period, as Kirinmaru arrived back from the battle, Zero was surprised to see her niece Rion back, and thinks that the battle is terrible for her. As Riku was made, the bugs has arrived on his right arm and she ordered him to dispatched it at the Bone-Eater's Well. Not too long after, Zero and Rion accompanied Kirinmaru as he slaughtered an entire kingdom as the samurai tried to kill him by the orders of Emperor Daigo. Rion was hiding behind Zero and clutching her robes when Sakasa, who's going to avenge his master's death grabbed her and held his sword to her. Kirinmaru effortlessly decapitated Sakasa, but Sakasa was a half-demon, who could still control his headless body. Sakasa's head has his body stabs Rion through the chest, killing her.

A century later, at the manor of Sesshōmaru's mother's where they waited for Tōga and her little brother Kirinmaru as they're going to destroy the Grim Comet. It is unknown that Zero and Kirinmaru have the Shikon no Tama. In 1297 in the Kamakura period, she and Kirinmaru have heard from Kyūki and Konton that they reported that Tōga have been spotted in Kamakura as he has been escaped grave injuries from battling with Shishinki and Ryūkotsusei.

She was foretold by the Shikon Jewel that her younger brother would ultimately be felled by an existence that is neither human nor demon and an impossible entity surpassing time itself. Due to her unrequited romantic feelings for Tōga, upon learning he died, while protecting his human wife Izayoi and his newborn half-demon son Inuyasha, from her old guardsman samurai Takemaru of Setsuna at the her burning mansion, she shed a tear upon the Sacred Jewel, wishing for her emotions and all her demonic powers to be cast away, which brought upon the Rainbow Pearls containing all her emotions and demonic powers. Those pearls were then scattered throughout the lands to ensure that a supreme demonic power would never ever be used fully.

When Sesshōmaru sired half-demon twin daughters and Inuyasha was to have a quarter-demon child, she suspected they could be the prophesied ones to defeat Kirinmaru, therefore she ordered two of the three princesses to be destroyed. After the Grim Comet has been destroyed, Zero found Rin and forged a link in their life forces, preventing Sesshōmaru from killing Zero without killing Rin as well, by using the Silver Scale Curse to find half-demon twins. Zero eventually found the twins Towa and Setsuna four years later, having tasked Homura to burn the forest in which they were living to eradicate them with Sesshōmaru unable to intervene, lest he kill his beloved Rin in the process.

During the story
As Zero stole the strong spiritual ability of sealing from monk Miroku, she had found something quite interesting, as Moroha is one quarter-demon, after Kirinmaru mentioned that she become Beniyasha from applying Tōga's blood to her lips. She was talking about the half-demon, including Setsuna.

Two hundred and fourteen years later, Zero returns to the site of the Great Dog Demon's demise and looks down on his ashes that were still imbued with his immensely powerful demonic strength and abilities. Recalling Tōga's last words to her after he and Kirinmaru stopped the Grim Comet, she takes his statement of never stop being who she truly is to heart. She asks Riku as to what must be done to force Towa tap into her innermost demon self to judge the elder half-demon twin's latent demonic abilities for herself. She decides to take Riku's word for it of Towa being far too kind for her own; that she would never be capable of harnessing the destructive power Zero desired.

Since severing all of her sisterly ties with Kirinmaru, Zero has since sought refuge to enact her own long-cherished whims from within a castle with a pink bow adorning the roof and doors. She had since then easily retrieved her Orange, Silver, Gold and Red Rainbow Pearls and was ready to absorb all of her respective demonic powers into herself to finally eradicate the Half-Demon Princesses from the earthly plane of existence. She is not pleased with Riku's sudden reappearance, though she thanks him for giving back the Green Rainbow Pearl he had just retrieved from one of three demon brothers who where battling Setsuna.

Wanting to further taunt Riku, she uses him to inform Kirinmaru of his failure to keep her precious Rainbow Pearls from her. Seeing how confused Riku is as to how she is communing with Kirinmaru so easily, Zero informs the demon-pirate about his origins that neither Kirinmaru or the Four Perils had been "nice enough" to tell him: That he was originally one of Kirinmaru's own slanted horns that was cut off by none other than Tōga during one of the rival beast kings many intense battles, six centuries ago. She scornfully tells a slightly shocked Riku to never come to her again; otherwise she would kill him without a second thought.

Once alone, Zero prepared herself to absorb each Rainbow Pearl back into her eyes from which they came as tears for ultimately using Tōga, whom she had loved so, both to a mere mortal woman and then to death itself. While looking the orange Rainbow Pearl, she can see Tōtetsu eating monks and so glad. Recalling that her red Rainbow Pearl was entrusted to the late Tōkotsu of the Four Perils, she absorbed it back into her left eye. It was then that she saw certain memories that shocked and infuriated her; of Inuyasha and Kagome bequeathing the shell rouge that retained remnants of not only Tōga's demon blood but the residual essence of Izayoi as well. Once absorbing the golden Pearl, she then witnessed a memory of a cold Setsuna meeting Towa for the first time in the modern era. Enraged that even one memory of the Half-Demon Princesses was absorbed to join her immense demonic strength and abilities as an unforeseen side effect of the Rainbow Pearls, she deduces that the placing of her Gold and Silver Rainbow Pearls within the eyes of his newborn twin daughters' was all Sesshōmaru's own design from the very beginning, now coming to the shocking realization that Sesshōmaru had foreseen everything she had every accomplished up to this point. Zero leaves the temple with the crystal ball, as Rion visits her from the crystal ball.

Zero then traveled to Nanahoshi's mansion in her Otsuyu disguise. Zero feigned weakness and asked Nanahoshi what he would like in return for granting her a wish. Nanahoshi opened the mini galaxy and sent one of it's orbs to detect the sorrow in Zero's heart. He was dismayed to find there was none, and Zero shed her disguise, explaining she sealed her emotions in the Rainbow Pearls. Zero then sent the pearls to surround Nanahoshi, and trapped him in an electric barrier. Nanahoshi asked Zero what she was going to do to him, and Zero said she was going to set a trap with his help.

On the night of the new moon, Zero sent her lantern butterflies to find Towa, who would be in her human form. Towa was transported to Nanahoshi's mansion where he placed the Eternity Bug on her and fed off her sorrow as Zero encouraged Towa to cry. Towa finally shed tears as she regained her demon powers. Nanahoshi then used his illusionary magic in combination with the Rainbow Pearls. Zero forced Towa to relive her misery of being alone in the modern era, and how Setsuna had forgotten about her. This caused Towa to turn into a full demon, and Zero was delighted to see the essence of Tōga in her. Towa destroyed the Eternity Bug and then Nanahoshi. Riku and Rion arrived as Towa went to attack Zero. Riku got in the way, and blocking Towa's strike. Zero then reabsorbed the Rainbow Pearls to restore he demon powered and declared she would send Towa to hell herself.

Zero continue to attack Towa and egg on her, revealing that she was the one who had Homura burn down the forest. However, Setsuna arrived and saved Towa by revealing that their mother had stolen her memories and now she remembers Towa as her sister. As the sisters tearfully embrace, Zero is dismayed that Towa won't attack. In fact, Towa thanks Zero for allowing her to go to the Reiwa era and meet all the people there. Tōga's spirit rises behind Towa and tells Zero it is all thanks to her. Furious, Zero tried to stab herself in the neck with her staff to kill both herself and Rin. In the nick of time, Setsuna finds the thread of fate that connects Zero to Tōga's spirit. Setsuna severs it, releasing Zero's memories, and destroying the Rainbow Pearls. Zero's emotions return once more as she breaks down and shames herself for Tōga's death. Tōga's spirit reassures Zero and reminds her to keep being who she is. Freed from her anger and past regrets, Zero commends Towa for being like her grandfather, and thanks Setsuna for untangling the thread of her heart. Zero willingly severs her ties with Rin and releases her from the silver-scale curse since she has no more regrets. Rion approaches Zero, and asks her to help them stop Kirinmaru. Zero apologizes to her niece and says this is goodbye. She then calls Riku's name, who stabs her in the chest. Riku sobs as he asks for Zero's forgiveness, but Zero thanks Riku. Before dying, she reveals to Towa and Setsuna how Rion died, and that is why Kirinmaru hates half-demons. Through her staff, Zero tells Kirinmaru that these half-demons are not the ones he hates, and that though he was prophesied to be felled by a half-demon, they may be able to save him or Rion. Zero says goodbye to her brother and says she'll wait for him in Nirvana, before her body disintegrates into sparkles. Her staff falls to the ground, restoring the flowers around Nanahoshi's mansion as Zero's spirit talks about how if a hopeless demon can fall in love with another demon, then she doesn't see why a demon can't call in love with a hopeless demon, and thinks the Half-Demon Princesses would agree with her.

Zero's premonition ultimately came true when Kirinmaru and Rion were reconciled and set free from their earthly bonds by Setsuna the same way Setsuna had allowed Zero to pass on. They then joined Zero as a reunited and reconciled family.

Personality
Zero is mysterious demon who is quite calm whenever disaster and death is afoot, similar to Sesshōmaru whom she has a connection with. It seems that Zero is also loyal to her brother and is ready to ruthlessly destroy any threat in his way, even innocent children.

Zero had feelings for Tōga and cried upon learning of his death, weeping inconsolably and wishing the Shikon Jewel take her feelings away. It granted her wish and created the Rainbow Pearls as a result. She appeared to be somewhat amnesiac after this, as she didn’t seem to remember what she had done afterwards, but did not question her confusion further. Due to not being chosen by Tōga, Zero resents those who have inherited his blood, especially those who also are part human. She especially appears to resent the ones he was romantically close to.

At present time, Zero is cryptic, detached and unreadable. She doesn't seem to have much interest in anything, reacting to most things with apathy or even nihilism and at many times acting in a contradicting manner. Although concerned for Kirinmaru's safety as the demon princesses are a threat to him, she also willingly toys with them and even provokes them into exhibiting their true powers for seemingly unknown reasons.

Deep down, Zero has lost faith and desires to be terminated, although her motives to seek death are centered more on causing Rin's death as a result and thus bring immense pain to Sesshōmaru. In fact, the bulk of Zero's actions towards the Half-Demon Princesses seem to be more focused on inflicting as much misery as she can in her wake, although she gloats of this as simply "being herself".

She was extremely furious when she learned Riku was gathering the Rainbow Pearls to return them to her, but was more than willing to use them to destroy the girls for good. Although she found relief and joy when she was temporarily killed by Setsuna, even trading insults with Sesshōmaru's mother, she was enraged when the latter pointed out that Zero was acting on jealousy and thus behaving like a human. Additionally, she acts on her rage once more by looking for the Rainbow Pearls purely to make Tōga’s remaining family suffer. This could point to Zero being a person who mainly acts on her emotions (even though she ironically no longer possesses emotions).

However, after Zero gained back her emotions thanks to Setsuna who severed the thread of fate connecting her to Tōga and he comfort her, she started to changed for the better.

Physical description
Zero appears as a beautiful, tall and slim woman. She has very pale skin with pointed ears, green eyes like Riku's, and a large volume of graphite hair, which is bound up in the traditional Oriental style, typically worn by nobles, secured by multiple gold hair sticks. A similarly gold comb holds back her fringe while her hair at the back is folded up and secured with a blue, butterfly wing clip. She also has curved violet stripes beneath each eye, a magenta stripe on each eyelid, dark purple lipstick, and dark grey nails. Originally and now, the violet stripes surrounded her eyes.

As for her clothing, she wears a black coat with grayish purple trim that reveals her clavicles, and on the sides she has a couple of light grayish purple butterflies with grayish purple accents embroidered, underneath she has a navy blue kimono and in front of the coat she wears a large light grayish purple ribbon (or bow) with dark grayish purple squares and tips attached to her waist. Zero also wears a white hadajuban, common tabi (socks), and black okobo with blue hanao.

Powers & Abilities

 * Like her brother, it is unknown if Zero possesses a true yōkai form, like Tōga, Sesshōmaru, and his mother do. She is currently in humanoid form, as she had formerly relinquished all her demonic abilities into the seven Rainbow Pearls.
 * Longevity: As a demon, she is capable of living for many centuries and has remained unchanged between the two times the Grim Comet traveled close to Earth - which has 500 years of difference. Surprisingly, despite her demonic power having been removed from her, she was still able to live for many more years after Tōga's death with no change to her physical appearance, suggesting she used some kind of magic to prolong her life, though Sesshōmaru's mother was not surprised when she finally died, suggesting she would have died eventually anyway.
 * Demonic Puppetry: Zero used a black swirling smoke to possess a demon puppet and since Sesshōmaru cut down, it came out and hearing her voice warning about the return of the Grim Comet after the lunar eclipse concluded. A feat that was revealed when Sesshōmaru cut her down with his Bakusaiga.
 * Spiritual Power Absorption: When she encountered Miroku, she was able to easily drain him of the strong spiritual ability he had used to seal Setsuna's innermost true demonic self and abilities.
 * Levitation: She can hover motionlessly above the ground.
 * Azusa no Yumihari: A webbing-like ability that acts as a strong binding agent that not only restrains movement, but also links the fate between said caster and target themselves with the threads of fate; namely young Rin in Episode 27 and, at one point, Towa. The thread is unstable, which even capable of withstanding Moroha's Crimson Backlash Wave.
 * Curse Inflicting: Zero has a special scale called the "Silver Scale" that once cast upon another, human or demon alike, it can inflict a curse call that will grow and cover the victim's entire body, ultimately killing them. Zero uses this to curse Rin which can cause the third and final death for her (including that Kirinmaru tries to assassinate Kagome and Inuyasha). But she tells to Sesshōmaru in Episode 27, that if they give the location of their half-demon twins, the curse of the silver-scale will be broken so Rin will be free. According to Rin, the silver scale curse is actually her lingering grief and regret for not being able to protect Tōga in his time of dire need, ultimately leading to his demise along with the mortal man Takemaru.
 * Lantern Butterflies: By conjuring a flock of said butterflies, she used them as her eyes and ears to find Towa's whereabouts.
 * Teleportation: By casting a strong spell combined with said butterflies, she was able to abduct an entirely powerless, human Towa by teleporting her to Nanahoshi's mansion.

Demonic Abilities
Upon the impulsively rash creation of the seven Rainbow Pearls from her tears to grant her wish to the Shikon Jewel, Zero's demonic power, along with her heart and grief, were stored away into the seven pearls. She even renounced her identity as a demon. Although just how powerful of a demon she was has not been stated, she was confident she could kill Towa, Moroha and Setsuna with her demonic powers restored and both Sesshōmaru and Kirinmaru would not allow her to use her respective demonic powers against them, suggesting she was an extremely powerful demon, especially as she was also a daiyōkai, though Kirinmaru seemed to still be incredibly strong, as he was able to confine all seven Rainbow Pearls and scatter them across various regions, despite Zero's presence capable of detecting and reclaiming her extraordinarily strong, respective demonic powers within each of them. She later absorbs all her seven Rainbow Pearls to gaining access her demonic abilities once again.


 * Rainbow Butterflies: Zero was capable of releasing colorful butterflies. She can only seem to do this once she restores her full demon powers with the Rainbow Pearls.
 * Yellow Dragon: The butterflies are able to merge into a dragon.
 * Demonic Energy Orbs: Zero was capable of releasing large energy balls. She can only seem to do this once she restores her full demonic powers with all seven of her Rainbow Pearls. She can launch a multitude all at once at incredible speed and angles. However, a fully demonic Towa was capable of shattering these powerful orbs relatively easily with her fully demonic energized broken Kikujūmonji replica.

Weapon

 * Staff: Zero wielded a tall scepter-like staff that has a spider emblem on it. It can shoot spider webs and blasts of violet energy from it. It is what is later known as the Azusa no Yumihari. The staff can be levitated and used to communicate Kirinmaru. It also has a point end that can be used to stab and impale if need be as seen when Zero attempted suicide by sending the end of staff towards her neck. Upon her second and final departure to the underworld, only it was left of her.
 * Rainbow Pearls: Zero was capable of using the Rainbow Pearls themselves to trap Nanahoshi in an electric force field. Later, she merged the pearls with herself to restore her full demon powers.
 * Nanahoshi's Fan: Zero used Nanahoshi's fan in Episode 34, and her final current physical appearance.

Relationships
Kirinmaru, lord of the eastern mainland is her younger brother. Once awakening him from his centuries slumber, she informs him about Sesshōmaru's decision to take a human as a bride just like Tōga married Izayoi, which naturally surprises and disgusts him. She then reminds her brother about a prophecy predicted by the Shikon Jewel before it was disintegrated that will bring about his inevitable demise at the hands of beings that are neither human nor demon, and an impossible entity that surpasses time itself. She appears very loyal to him, and appeared to have a good relationship in the past when Kirinmaru and Tōga destroyed the Grim Comet, but it is unknown what their true relationship is today or if Tōga had any impact on this.
 * Kirinmaru

At present Zero seems to be behind the bulk of Kirinmaru's actions being the central planner behind trying to get the Half-Demon Princesses killed, to which he responds with mild amusement at best. Kirinmaru is unnerved by Zero's malice and cannot stomach his sister's dishonor as she sinks to new lows ever since she made her wish, as she tries to spread misery. She subsequently disowns Kirinmaru after the latter easily dispersed her Rainbow Pearls across the regions of feudal Japan. Once managing to reclaim the Silver, Gold, Blue and Orange Pearls, ready to reabsorb her varied, strong demonic powers back into her body, she had used Riku to send her brother her cryptic message in doing so with ease, that she had easily foiled his plans in stopping her.

Zero and her niece Rion appeared to be quite close, Zero being quick to comfort Rion after she saw her father's first defeat and admonishing Kirinmaru for repeatedly bringing her into the battlefield. Even in the present, she seemed to still retain fondness for her niece, affectionately referring to her as her "dear niece" and admitting she was pleased to see her once again after she escaped Mount Musubi, along with stating she'll consider stopping Kirinmaru, even expressing some concern when she realized Rion will try to stop Kirinmaru.
 * Rion

In Episode 22, Tōga was a good friend of hers right after he and Kirinmaru destroyed the Grim Comet, stating Kirinmaru was lucky to have Zero for a sister. In Episode 15, Zero stated that she had strong feelings for Tōga, but the dog daiyōkai humiliated her, leading a massive revenge plot towards the Great Dog Demon's whole family, including Sesshōmaru, his half-demon daughters Towa and Setsuna, Inuyasha, and his quarter-demon daughter Moroha. When the Great Dog Demon lost his life that he fought Takemaru, Zero grieved deeply as she believed that they were meant to walk the path of eternity together; a destiny that the Shikon Jewel itself had prophesied. This is what caused her to seal away her emotions and demonic powers, although since she seemed to forget her actions after the deed was done, it is unknown if she fully remembers her history with Tōga. Due to her past feelings for him, Zero was naturally jealous of his former mate and possibly even Izayoi, which only further inspire her to take revenge on his family. In fact, her actions today still originate from the heartbreak Tōga caused her, and is forever resentful of him because of this. Sesshōmaru’s mother, after implying a sense of pity for her, comments that Zero is a woman who burns from love, further shedding light on Zero’s character and her feelings for Tōga. In Episode 36, as Towa's demonic blood has been awakened, Zero has been delighted to see her along with the spirit of her grandfather Tōga that "her bloodlust is like that of the Great Dog Demon!". In Episode 37, Zero saw that Towa takes demonic energy projection of her grandfather Tōga in which she was excited as she said, "My Lord." After the thread of fate between her and Tōga have been severed by Setsuna's Yukari no Tachikiri, she was stop by commits suicide and felt from her tears.
 * Tōga

The two knew each other 500 years ago around the time Kirinmaru and Tōga worked together to stop the Grim Comet, with Sesshōmaru’s mother being Tōga’s mate at the time and Zero being Kirinmaru’s sister. Being in love with Tōga, Zero naturally felt envious of Sesshōmaru’s mother for having his affections, and as such the two had a mutual dislike of each other. Both of them seem to be aware of the other's feelings over Tōga's death, Zero noting she could tell Sesshōmaru's mother despite her haughty demeanor did feel some sadness and grief over it and felt bitterness towards Izayoi for both taking his heart and causing his death, which she didn't outright deny in the former regard and coldly stated she had no regard for humans for the latter regard, while Sesshōmaru's mother was also aware that Zero hunted down her granddaughters and sought to cause her son pain by linking her life to Rin so when she dies, so does her daughter-in-law, out of irrational jealousy. Clearly displeased with Zero when she revealed her sadistic glee at the idea of her son's suffering and having previously shown disapproval of Zero's relentless desire to kill her granddaughters, she proved to be able to affect Zero more than she affected her, sarcastically stating Zero was almost human-like for her jealousy and making her angry. At the same time, she seemed to have some pity towards Zero, calling her pitiful for being a "women who burns from love".
 * Sesshōmaru's mother

It seems that she does not care about him much, thinking that he is an indolent person. She did not seem pleased that her brother had been leaving the situation in his hands, as she may be aware that Riku is after all seven Rainbow Pearls. However, it was revealed she cared for Riku in the past after Kirinmaru discarded him, so Riku appears to be highly devoted and loyal to her. She was angered when she learned he was gathering the Pearls for her, but nonetheless used this to her advantage.
 * Riku

Having sought refuge in a castle covered with a large bow on its outside, Zero expressed her disdain at his unexpected reappearance, even though he had returned the Green Rainbow Pearl to her. To taunt him further, she revealed the truth of how he had been brought into existence: That he was originally one of her brother's own horns atop his forehead that had been broken off by Tōga himself! And that because of him literally being nothing more than a crucial part of Kirinmaru's physical self, she could freely converse mentally with her brother through Riku's now human-like eyes and ears alone.

After her ties to Tōga were severed, Zero asked Riku to put her to rest to which he tearfully complied.

Zero's relationship with her younger brother's minions has not yet been explored. She heard the news from Kyūki and Konton that Tōga did battled with Shishinki and Ryūkotsusei. However, she seems to value them more than her brother, being displeased with his apathy towards the deaths of Tōkotsu (including his son Jakotsumaru) and Kyūki and refusal to engage the Half-Demon Princesses after they killed them.
 * The Four Perils

Many months later, she finally reclaimed her bright Orange Rainbow Pearl and thus was able to glimpse a brief memory of the last one to possess it; that being Tōtetsu. From taking back her own demonic abilities that the Red Rainbow Pearl contained within, Zero recalled that it had once been entrusted to the now late boar demon Tōkotsu. She was thoroughly shocked and infuriated to discover that her Red Pearl had only horded memories of what had befallen Moroha's parents but of her lifelong romantic rival, Izayoi as well.

Enemies
She has known Tōga's eldest son for many centuries. Finally aware of his decision to take a mere human woman as a bride, just as his father had, she eventually reappears before him and expressed her interest and disdain in siring half-demon twin daughters of all things. She had been searching for the twins who will bring about her brother's destruction for four years, and succeeds via the dream-gazing spell. She then orders Homura the mountain god of the northern mountains to burn the entire forest and destroy Sesshōmaru's daughters, making sure that he cannot intervene to save his young twin daughters from her or her younger brother's wrath. She later interacted with him again after being slain in battle with his twins, but Sesshōmaru revived her with Tenseiga afterwards. This was purely so as to prevent Sesshōmaru’s human wife Rin from dying, as Zero previously cast the silver-scale curse that tied her and Rin’s life together, so if Zero would die, Rin would go with her. Zero appeared happy in her final moments, knowing Sesshōmaru would lose somewhat he loved, implying a sense of hatred towards the daiyōkai (possibly due to his relation to Tōga), but this turned into immense anger towards him after her resurrection. This anger caused her to act by attempting to reclaim her demon power and destroy his twins, but was stopped by Kirinmaru, who scattered the Pearls across Japan once more. Sesshōmaru, realizing the danger Zero is and knowing that Rin would rather die than let any harm befall their daughters, sets off to kill Zero in order to prevent this from happening, even though this meant he would have to let Rin die in the process.
 * Sesshōmaru

The two have most likely never met before, although Zero knew of her, no doubt. She speaks of Izayoi in a disdainful manner when speaking with Sesshōmaru’s mother over her, implying and revealing a sense of hatred for Izayoi. Because Izayoi became Tōga's second wife, it is undoubtedly the sole reason why Zero would hate her so much, since she herself had feelings for Tōga and Izayoi inadvertently caused Tōga's death, since he died saving her in her burning mansion that he fought Izayoi's old guardsman Takemaru of Setsuna that she didn't know.
 * Izayoi

However, Zero does not give much thought to the human, and instead focuses her energy on ending the rest of Tōga’s bloodline, including Izayoi's own half-dog demon son that ultimately led to the birth of a daughter with twenty-five percent of the Great Dog Demon's pure demon blood flowing in her body, which further infuriated her aim to wipe out the longtime deceased mortal noblewoman's only remaining relatives: Her full-grown son and feisty teenage granddaughter.

Zero knew that Sesshōmaru is married to Rin and plotted to go after her, being the human mother of Sesshōmaru's twin daughters. Following the destruction of the Grim Comet, Zero appeared before Rin. Saying that she couldn't allow a human woman to be loved by a demon, she placed a silver-scale upon Rin's neck, therefore intertwining their fates.
 * Rin

To keep Rin from succumbing to the silver-scale curse, Rin was sealed within the Sacred Tree of Ages. However it is implied that if Zero is killed, Rin will also die with her. This was revealed to be true, as Zero was happy upon nearing death, since she knew that even though she would perish, Sesshōmaru would still lose someone he loved.

After her thread of fate was severed, Zero undid both the thread of fate connecting her to Rin and the Silver-Scale Curse. Upon her passing, a field of flowers bloomed in Nanahoshi's mansion as a sign of apology to Rin.

Zero is the one who wishes to end the lives of the three girls, out of fear of the Shikon Jewel's ominous prophecy coming to fulfillment. She undoes the seal that restrains Setsuna's demon blood by controlling Towa with the intention of giving Kirinmaru a reason to go at them at full power. She later asks Riku as to awakening Towa's hidden powers. She referred to Towa and Setsuna as "Half-Breed Pups." After Setsuna severed her thread of fate with Tōga, Zero let go of her vendetta against the twins as Towa reminded her of the Great Dog Demon and Setsuna released her from the regret from over 200 years ago.
 * Towa, Setsuna and Moroha

Trivia

 * As the Shikon Jewel tends to twist the wishes of its user, it's more likely it only sealed Zero's positive feelings within the Rainbow Pearls, as opposed to all of her various demonic abilities; explaining why she is so sadistic, spiteful, cruel and nihilistic (even by a daiyōkai's standards as Kirinmaru is polite to others he barely acknowledges).

Media appearances
Zero Zero