|“||Hey--this Big Sis--may I kill her?||”|
Mariko first appears when released from her isolation chamber, with Saito greeting the emaciated little girl upon her emergence, believing they had built up a mother-daughter relationship. The little girl proved her handler naive when she rejected this idea, tearing the scientist apart and sending her upper torso through the control station's glass partition to prevent them from stopping her. The dying Saito pressed a button that set off one of the explosives bound into her body, blowing off her right arm. Shirakawa and Kurama's assistant, Isobe, then took over her handling and warned her of the other explosives to keep her under control. It was Shirakawa, jealous at Kurama's daughter with another woman, who suggested the embedded bombs as a control, though like as not the Chief would have initiated some mechanism even without her. Feeling that his disobedience in not killing the injured Nana violated the agreement to protect her, Chief Kakuzawa sent her and her handlers off to exterminate Nana and capture Lucy/Nyu. While preparing Mariko for the mission, Isobe learned that the late Saito had only told Mariko part of the truth about her parents. The scientist/controller indicated that both of her parents had rejected her entirely, when in fact, only Kurama had initially, later making a deal that kept him tighter on the Chief's leash in exchange for her life, the last wish of her dying mother. Isobe became angered at this, realizing that Saito wanted to be Mariko's sole parental figure for reasons of control, for all the good it ultimately did her. Shirakawa indicated that an unspoken desire of Mariko's could be brought about by her obedience, perhaps being reunited with the birth parents she had never known. This idea is not elaborated on directly, nor mentioned again, though, in fact, she did meet her surviving parent.
She was sweet and innocent in some respects and yet had no qualms about lashing out at all humans, especially those she saw as tormentors, and even fellow Diclonii. While not stated directly, her containment chamber was said to be a dangerous place, indicating that some Institute personnel met their end near there. It also seems possible that her more elaborate containment area was like the one prepared for Lucy herself, just before her escape.
Transported to the Enoshima Park Beach boardwalk in a wheelchair (her limbs atrophied from her captivity), she saw Nana approach them, Nana having sensed her presence and not wishing to endanger her new friends at Maple House. Mariko immediately showed that she regarded killing as a game. When Nana extolled the virtues of her 'papa,' she angrily rejected her own and resented her for having one, not realizing both were the same man. Stripped naked and played with like a doll (Nana's artificial limbs coming off, as they often did), Nana seemed to accept her fate until Mariko made a threat to Nana's unseen Papa, which enraged Nana into action.
Though overpowered by Mariko, Nana managed to use her unique ability (as she once had on Lucy) to disable her vectors. Kurama then showed up, almost ignoring Nana for Mariko, his real daughter, while explaining how this all came to pass. Mariko had by this point manipulated Isobe into giving her the control device for the bombs, but could only delay them, not disable them entirely. A military bombardment (possibly directed by Kurama's new allies in Saseba) followed, which Mariko saved them from while briefly becoming an amnesiac like Lucy, saying 'Myu.' Nana prevents Kurama from executing the now-helpless Mariko. During the fighting, Lucy showed up, first as Nyu, having followed Kouta to the beachfront and then bypassing police blockades to get to Nana, who Nyu saw as her friend. When Shirakawa arrived on the scene, she informed Kurama that Chief Kakuzawa's ultimate plan was about to be enacted, causing a panicked Kurama to seize Nyu as a hostage, to threaten a pillar to Kakuzawa's plans and thereby delay him. Attempting to execute Nyu once and for all, Kurama's bullet caused her to reawaken as Lucy, who promptly killed Shirakawa and wrecked the control device for Mariko's body bombs, making their explosion inevitable. Kurama briefly bonded with his daughter, apologizing for not being the kind of father she deserved. Mariko, accepting her fate and her father's love, urged Nana to take care of him before facing the less powerful, but much more experienced Lucy for the last time. Although dismembered and finally decapitated by Lucy, the explosion of the bombs inside her also wounded Lucy and forced Nyu's personality back to the surface. Before losing her head, Mariko declared again how she loved her father. Nana later weeps at all the beautiful things in life that Mariko will never know, and sees her in a dream walking with Kurama into the afterlife. Kurama for a time goes insane from the grief accompanying Mariko's loss, attempting suicide and seeing two of Mariko's clones as his lost daughter, even viciously spurning Nana, who refused to leave his side once she found him again. But when one of them actively threatened Nana, it was enough to shake off his stupor, killing the clone and at last moving forward.
In the manga series' conclusion, Kurama and Nana are seen at her grave, burying her ashes. Presumably, these are the ashes of those parts of her that could be recovered, after the explosion.
Most of the known facts about the manga version of Mariko apply here as well, but some definite differences exist.
For example, whether this was part of the unspoken plot or not, no aspersions are cast on Saito's motives, and her actions while dying seem decidedly more heroic. Isobe is a good deal colder regarding her case and in other matters, while Shirakawa was the one disturbed by placing bombs in the body of a small child. Mariko played with Nana as she did in the manga, but in this instance, Nyu was accompanied by Kouta, when they found the police blockade rendered unconscious. Mariko briefly threatened Kouta, though Shirakawa was more interested in why a Human and a Diclonius had any relationship at all. Mariko, now doubly enraged by Nana even having friends began to strangle Nana. In desperation, Nana disabled Mariko's vectors before collapsing through a guard railing on the bridge where the battle was taking place. Just as with Nana, the innocent Nyu personality does not register as Lucy to Mariko, who also tearfully announces that her vectors are disabled. Isobe withdraws with Mariko, leaving the soldiers to attack Kouta and Nyu, which re-awakens Lucy and dooms Shirakawa and every soldier present.
At a nearby position, Isobe is informed by the Chief that even a powerless Mariko can be of use, perhaps indicating the possibility of clones in an unrealized anime second season. Unknowingly, Isobe's conversation informs Mariko of her family name and who her father is. Nana, who was recovered by Kurama, pleads with him not to kill Mariko, but Kurama seems resolved.
Recovering after a time, Mariko kills the soldier guarding her and goes to seek Lucy, whose presence she senses. If Lucy was able to use stealth and cunning to win the day in the manga, this all-out open raw battle went quickly to Mariko, though it is possible Lucy, dispirited by Kouta's anger at his returned memories, displayed. This revelation is an event that occurred well after the manga equivalent of Mariko's story arc. Finally breaking one of Lucy's horns, Mariko stops, halted by the announced presence of Kurama. At first overjoyed to see him at last, Mariko quickly lapses into despair and rage when she realizes he is there to kill her, calling out his hypocrisy and cruelty in dashing the only dream she has ever had. Enraged, she attempted to kill Nana, who had so much more than her, including their father's love. Kurama embraces Mariko and apologizes for how little of a father he has been. Mariko learns that her mother always loved her and that her father now loves her more than life itself. Bidding Nana goodbye, Kurama orders Isobe to ignite the bombs. As the seconds tick away, the pair imagines a blissful life if Mariko had been born without horns, till the explosion takes them both.
Once back at Maple House, a tearful Nana remembers both Mariko and Nyu (supposed dead at this point) who will never know all the wonderful things the world has to offer. The lack of a second season meant that any future plotlines involving the Kurama family would never come to pass.
At first, Mariko appears to be the typical sort of Diclonius those who work at the Diclonius Research Institute expect them to be. Toward human beings, she was sadistic and didn't hesitate to kill anyone who came near her. This animosity extended toward Saito, who at that point endeared herself to her enough for Mariko to refer to her as "Mommy" before realizing Saito was not her mother. Only the threat of pain kept her in line, and rather than show malice toward her handlers; she expressed a childish excitement toward maiming the other diclonius she would be allowed to fight.
Her sadism, however, is only a portion of her being and is likely a front caused by the various traumas during her very short life. Beating Nana up and taking her limbs off is little more than a game to her, like a child "tearing the wings off an insect" in the words of Shirakawa. She only appears to realize the strength of her powers regarding how it can help her. That empowerment can take the form of escaping from her tormentors. It could be taking revenge on them (such as during her initial introduction). She could see it all as a game (fighting Nana), or as a way to protect herself or her family (fighting Lucy, beating up Nana out of jealousy in episode 13), yet can only take her so far. She's incredibly precocious as well, able to trick Isobe into giving her the cell phone code to postpone her bombs' detonation and killing him afterward in the manga.
Underneath the vicious nature she developed from being imprisoned in the research facility, Mariko is still, at heart, little more than a 5-6-year-old girl who wants nothing more than to be with her family again. This desire leads to her being selfish regarding what she wants and also makes her jealous of those who have what she does not. This envy shows itself best when she interacts with Nana. Mariko is initially envious of Nana having friends at all when she's a Diclonius like her, and this envy morphs into outright jealousy when she learns of Nana and Kurama's father-daughter relationship, finding it unfair since Kurama let his real daughter be locked away in the darkness. Naturally, she takes her aggression out on Nana and taunts Kurama in doing so as a way to punish him for abandoning her and favoring another girl with horns. In both manga and anime, though, Mariko does reconcile with her father before dying. In the manga, she asks Nana to take care of him before sacrificing herself in an attack on Lucy, and in the anime, both father and daughter die together after Kurama apologizes for abandoning her.
Myu is the noise she would make after deflecting a missile that was fired to kill her and is used to describe her resulting split-personality. Both she and Kurama would have died so she used her vectors for protection and the result was a loss of memory. She was sweet and calm with reactions the same as a three-year-old girl and behaved just like would have if she wasn't a Diclonius. Unlike Nyu, she couldn't use her vectors.
Later, while docile under the influence of mind-control devices, the four viable clones of Mariko, Alicia, Barbara, Cynthia, Diana, also made the 'Myu' sound and showed extraordinary loyalty to their 'creator,' Nousou. The devices when removed from two of them, made them revert and showed the most vicious and bloodthirsty aspects of Mariko's personality, and a deep rage at the treatment they and their kind had endured. To varying degrees, two of them showed some recognition of who Kurama was.
Vector Range: 11m in the manga (though they seem to be much longer in the anime)
Strength: Unknown possibly higher than average. Boosted by the sheer amount of vectors she possesses, 26 in the anime and 50 in the manga.
Speed: Slow, stated by Isobe.
Number: 26 in the anime and 50 in the manga
Vector Special Ability: Can vibrate so fast they become visible.
In the manga, the Institute made clones of Mariko, but it is unknown if their creation occurred before or after she passed. However, most were weaker with lower length vectors and, due to control devices implanted in them, found it harder to track other Diclonii. While under control, they also had infantile, dependent personalities and said 'Myu.' These were:
Cancelled Second Season Speculations
There are a few scenes in the last anime episode that have caused speculation that Mariko used her vectors to save Kurama from the explosion. This possible storyline is not able to be confirmed.
However, an alternate ending to the anime's final episode was scripted but not used. In this, Mariko did save her father, who returned to the Diclonius Research Institute, killed the Chief, and destroyed the island with himself on it via a missile the Chief had planned to use to spread the Diclonius virus.
- The 真理 kanji symbols in Mariko's name mean truth, making her name's full meaning "child of truth." Her name is also frequently spelled using katakana symbols, as is the trend for some of the main characters (i.e. Kouta, Yuka, Mayu).
- Mariko's Seiyu, Tomoko Kawakami, died as a result of ovarian cancer on June 9th, 2011.
- Mariko's English voice actress, Luci Christian, also voices her mother, Hiromi.
- Mariko appears by herself on a total of two manga chapter covers.
- Mariko's story arc's ending provides a pivotal moment for the manga narrative and the conclusion of the anime series.
- In the last episode of the anime, there's a minor graphical error right before Mariko unleashes a barrage of vectors on Lucy. Lucy knocks Mariko out of her wheelchair, dislodging her prosthetic right arm in the process, but when the camera focuses on the arm for a second, the limb appears to be a left arm.