Gokusai Kaibi

Gokusai Kaibi (獄彩海美) is a character introduced in Toaru Majutsu no Index, and featured in the sidestory Toaru Majutsu no Index SS: Biohacker Arc, from which her name was finally revealed.

For a long time only known as the Girl in the Dress (ドレスの少女) or Measure Heart, she is a teenage girl who participates in "" or compensated dating for money. She is an operative of SCHOOL, acquainted with the ways of the Dark Side of Academy City, and the second of the three Gokusai sisters.

Etymology
Kaibi's surname Gokusai may be translated from Japanese as "painted prison". Meanwhile, her first name can be interpreted as "sea beauty". The three Gokusai sisters share a pattern where each sister has a first name with a nature-based character; in Kaibi's case, it is the character for "sea".

Appearance
She is described as a beautiful girl in a showy dress with an open back that looks for about 14 years old. She has light colored wavy hair. She wears jewelry on her person. Her dress is said to be one would expect a woman from a hostess club would wear.

Personality
During missions she is very hostile to those she deems her enemies. However, she has displayed a certain amount of nobleness or mercy within the battlefield to those who are no longer a threat to her, or have gained her respect in the process, as with the case with Hamazura Shiage and Takitsubo Rikou, the former whom is willingly to face her and Kakine Teitoku in order to protect her from them. She also knows when to fold, as she has shown reluctance when an enemy who she cannot stand a chance against with her power, someone unpredictable with her power like Accelerator. She is also somewhat airheaded, positing a ridiculous question on how Shiage could have disguised himself as a mother, baby, or a baby carriage to her comrade. Outside combat she seems to act a little frivolous, using her showy appearance to earn extra money.

Background
As a member of SCHOOL, she takes part in Kakine's efforts in gaining an audience with Aleister and negotiating with him, though it is uncertain why. She partakes in "" or compensated dating for money with rich old men. According to her, there is nothing sexual involved - just her providing company to her customers. She states that her customers are looking for relationships that can be bought through money, and that she takes their money and give them some relief with their complexes. However, she does state that it depends on a case by case basis.

Daihasei Festival Arc (Railgun)
She is with Kakine Teitoku waiting for in a private hotel room when the SCHOOL liaison contacts Kakine regarding the Daihaseisai Planning Committee, under the orders of the higher-ups, to have the Level 5s do the opening demonstrations for the festival. Kakine naturally refused the request, but the liaison was quite persistent forcing Kakine on a rant regarding events such as the Daihaseisai as being for those who still believe in hardwork and hope. And the liaison references Kakine's preference in using angel wings, saying that he is the type that would appeal to kids and then laughing about it. Kakine did no take this into stride, he goes berserk and wrecks the room they were in.

When the Boy with goggles arrives, he asks what had transpired,and she explains it to him. Her explanation makes the Yobou chortle, but quickly hides it after Kakine asks him if he was laughing.

Battle Royale Arc
Becoming brazen enough after the HsPS-15 Powered Suits left to clean-up Avignon, SCHOOL apparently rebels against the higher-ups and participates in the citywide factional war of underground organizations on October 9 in order to gain an audience with Aleister Crowley.

Due to the effects by the assassination attempt on Oyafune Monaka, the security in the Elementary Particle Engineering Laboratory has been disrupted, allowing for SCHOOL to infiltrate it in order to steal the Tweezers. There they are intercepted by ITEM. Apparently not risking a battle, SCHOOL escapes the facility in a station wagon with ITEM close behind. It is unknown how, but the Girl is first seen operating a mobile crane with a wrecking ball to intercept ITEM's car that was chasing the station wagon Kakine was on. With her skills, she is able to hit the car, pushing it towards a wall. Mugino Shizuri explains to Hamazura Shiage that the ones who are attacking them are SCHOOL, wanting the station to get away. Kaibi backs up the mobile crane for about 10 meters as she tries to strike the car again. Seeing this, Mugino orders Shiage to smash the windshield of the car as it had crush the doors too much. They are able to escape the car just in time as Kaibi crushes it with the wrecking ball and later explodes. With the crane's engine apparently stalling, Kaibi comes down to go after them personally. Mugino tells them that they should split up. Shiage asks why she couldn't stay and fight, to which she says that she is after the Tweezers in the station wagon they were chasing, and does not care for subordinates like her. Furthermore, Mugino states that Kaibi's power is troublesome. With that they leave in different directions. Shiage goes into an alley between buildings but discovers Kaibi following him. He continued to run, climbing up an emergency staircase on one of the buildings. Entering a student dormitory, he keeps on running straight through a hallway but then hears a door open behind him. Kaibi catches up to Shiage with a small gun in her hand. Shiage then frantically pushes the button to activate the steel shutters between them, used for protection against out-of-control esper powers. Kaibi is shocked and tries to shoot at the shutters twice, but to no avail. The both of the looked at each other on the monitor next to them. As Shiage taunts her and Kaibi puts away her gun and takes out a 40mm grenade launcher. Horrified, Shiage runs along the hallway again as Kaibi launches a projectile towards the steel shutter. Shiage did not fully escape the blast as fragments him and propelling him 5 meters down the hallway. Finding his bearings again, he staggers to run away again and finds himself on a terrace with a three story drop below. Not wanting to face her, Shiage jumps down, exclaiming that being a loser is the best. He later sees a young mother pushing a baby carriage down in the alley. Believing he will crash with the carriage, Shiage helplessly swings his arms and legs around trying to get some distance them. He later lands 15 cm from the carriage. His appearance both shocks the mother and the baby, the former asking who he is, to which Shiage says that he is the kind of hero that falls from the sky. He then says that it is dangerous in their parts and advises her to leave before running down a nearby alley.

When Kaibi arrived at the terrace, she only finds the woman and her baby in the carriage. She later calls a comrade, reporting on how she has lost her target. She then says that there is mother and a baby carriage nearby and posits a question that Shiage could have disguised himself as a baby, a mother, or baby carriage. She was later called an idiot and told to die afterwards as a response. She is later annoyed by the fact that she let her guard down as she though Shiage was not too bothersome, and laments on how she should've used her powers from the start.

Later, after Frenda Seivelun betrayed ITEM's location to SCHOOL, Gokusai Kaibi and Sunazara Chimitsu accompany Kakine Teitoku to attack the Private Salon in School District 3. When Shiage returns back to Kakine after deciding to protect Rikou, he finds her collapsed before him. Here, he is surprised by Shiage's return. He tells Shiage that Rikou did well against him despite having no direct battle power. He tells Shiage that she must've used her search power to try to interfere with his AIM diffusion fields to reverse the flow and take control of his power. He then comments on how if Rikou developed more then she could've become the 8th-ranked Level 5. Having none of it, Shiage tries to use his handgun. But there, Kaibi arrives for backup and Shiage immediately recognizes as the "Crane Woman" from earlier. As Shiage struggles who to aim at, Kaibi then says that he should stop whatever he is doing. With those words, Shiage couldn't move his body. Here, Kaibi starts using her powers on him, to make him not shoot at them because it is seemingly against his nature. Seeing Shiage's struggle, Kaibi comments on how he may be fairly kind on the inside. She smiles and then says that her power Measure Heart she can freely regulate "the distance between people's hearts." She advises Shiage to stop fighting against them, as she has him set-up to make it seem that the distance between their hearts are the same between him and Rikou. He can't shoot her just as much he can't shoot Rikou. Seeing this display, Kakine begins speaking, saying that the situation made it seem like they were the bad guys. He comments on how Shiage and Rikou, a man and a woman, protecting each other is a moving story, and that it is such a rare sight that he feels that he shouldn't destroy it. He then tells him that Rikou will die regardless of what they do, shocking Shiage. Kakine kicks the Ability Body Crystal case towards him, and says that she was using the Ability Body Crystal to activate her powers. Kakine then explains the usage of Ability Body Crystal and on how it affects Rikou. Kakine tells Shiage that Rikou will not last long in her current state, stating that she'll be fine as long as she doesn't user her powers ever again. As Shiage is frozen in shock, Kakine tells him that they don't need to kill her if she can; use her searching powers and that he doesn't care if she died or not. Kaibi then tells Shiage that she collapsed on her own as she kept forcing on using the Ability Body Crystal in order to fight them, and tells him that none of her would be left if they attacked her seriously.

As Shiage stares them down after their revelation, he manages to press the button for the elevator. As Shiage waits for the elevator, Kakine wonders if he should kill or let her go. Kaibi says that they can just leave her alone as a member of ITEM on the edge of her doom can't stop them. Shiage grounds his teeth after what Kaibi just said, despite this he still can't attack her. Kakine says that it'd be easier to kill her, but Kaibi counters by saying that since Rikou used his AIM to mess up his Personal Reality, Kakine should check up on that. She says that his power going out of control would be much more dangerous than Rikou, and that she would rather not die if an ally of hers went out of control. Teitoko becomes annoyed at being bossed around, but acquiesces to Kaibi's warnings. He tells her that they should leave as though checking up is easy they don't have the necessary equipment. At that moment an elevator arrives and Kakine and Kaibi both leave with the recently arrived elevator, allowing Shiage and Rikou to escape harm.

Afterwards, Gokusai Kaibi accompanies a male scientist for an entire hour, though there was no sex involved as she just gave him company. She is later paid for her services, though she complains about the scientist not giving her a tip. She later receives a report on how ITEM has been destroyed by in-fighting with Mugino Shizuri being taken out. She later returns to one of SCHOOL's hideouts, where he meets up with Kakine again. He asks where she has been, to which Kaibi begins to immediately complain about scientists not giving her tips and only paying the basic rate. Kakine wonders and says that an hour isn't very long, but Kaibi says that she shouldn't be guilty as they were talking in the hotel room while she flipped through a magazine. Kakine asks if Kaibi doesn't do anything sexual, to which she says that she doesn't need to. She then explains her business to him. She then mentions to Kakine on the fate of ITEM and Mugino. This surprises Kakine, especially with Mugino apparently escaping his attack on her earlier. He asks on who was the one to have defeated her as Frenda betrayed ITEM and fled (now dead), him defeating Saiai, and Rikou not having a directly battle ability. But Kakine then trails in his words, realizing that it may have been someone from the subordinate organization. There Kakine and Kaibi recall Shiage back in the elevator hall who was trying to protect Rikou. Kakine then whistles in praise for him. Kaibi then asks about the analysis with the Tweezers. Kakine answers by referencing on how Aleister seems to know a little too much about their actions beyond the use of conventional surveillance technologies. He then says that Aleister does so by using UNDER_LINE after having spreading about ten million invisible machines throughout the city. He explains on how they needed the Tweezers to capture the microscopic machines that make up UNDER_LINE and get information out of it. The Girl then asks again regarding the results of the analysis, to which Kakine laments on how the date in UNDER_LINE it is not enough compared to Aleister. Kaibi then asks if he truly must kill Accelerator, to which Kakine confirms as it is the only way for him to ensure the negotiations with Aleister would go well. Hearing this, Kaibi states that she will not be taking part in a battle against Accelerator, explaining on how his reaction to her using her powers on him would be too unpredictable, and liable to get her killed. Hearing this, Kakine is not disappointed as he had expected that she wouldn't be much help in the battle anyway. Kaibi then looks again on the Tweezers and says to Kakine that if he has the result then she should tell her as she would like to know if they can directly negotiate with Aleister, to which Kakine agrees.

DRAGON Arc
She is a part of the new team that is established after the events of the Battle Royale Arc.

Here she leads the remnants of the Hound Dogs under the order of General Superintendent Aleister to eliminate Hamazura Shiage, as he was supposed to end up dead during the battle royale between the 5 organizations. The first thing that Measure Heart does is restrain her new teammate Kinuhata Saiai while the former Hound Dogs proceeded to track down Shiage. Gokusai Kaibi seems to be surprised that lots of troops are ordered and deployed for the sake of taking out a Level 0 that seems to have no true relevance.

Measure Heart
Her ability is known as Measure Heart (心理定規 (メジャーハート) ), an ability that allows her to regulate "the distance between people's hearts". Seemingly an application of Telepathy, it allows her to set herself at a certain "distance in the heart" with a target, allowing her to be either seemingly close in affection to her target or be distant from them. Reactions to this manipulation varies. For example: in one opportunity, she sets her distance to Shiage to the same value he has to Takitsubo Rikou, at which point Shiage is unable to shoot her, the same way he would not shoot Rikou, despite objectively knowing that Kaibi and Rikou are two different people. Here, Gokusai Kaibi also gives a hypothetical example with Accelerator, stating that he may be someone who would feel betrayed if she uses her power on him and display extreme murderous rage. This means that she has to be careful on in which level she sets herself when facing a target in order to get beneficial results. She can't measure the distance when the target is sleeping.

Her level is unknown. It is also described by Mugino, a Level 5, as a troublesome ability.

Others
Since her ability isn't used for direct combat, she uses a variety of tools and weapons to attack her targets, such as a ladies' gun or a small 40mm grenade launcher. She can also apparently operate heavy machinery like a mobile crane.

Quotes

 * (To an unknown SCHOOL comrade, most probably Kakine, from Volume 15): "I lost my target. There’s only a baby, a mother, and a baby carriage around here. …Do you think it’s possible that the man disguised himself as a baby, a mother, or a baby carriage?"
 * (To Kakine, ibid) "A guy and a girl protecting each other like this is such a moving story. It‘s such a rare sight that it makes me not want to destroy it."
 * (To Shiage, ibid) "You don't want your true feelings to be painted over with lies, do you? You should share the joy of living on with that dying girl."
 * (To Saiai, ibid) "It seems the irregular factors known as Kamijou Touma and Accelerator are within the allowable limit of irregularity. That is why they are at the core of the plan. When they struggle, it can be used to the benefit of the plan. I don’t actually know what the plan is, though. Incidentally, Hamazura Shiage is different."