Gokusai Kaibi

The "Girl in dress" is an Esper of unknown level who is a part of SCHOOL. Her ability name is Measure Heart. Her name has never been disclosed.

Appearance
She is usually described as a beautiful girl in a showy dress that looks for about 14 years old. , she seems to be interested in Kakine Teitoku's plan of negotiating with Aleister

Personality
She shows reluctance when fighting an enemy when she can not foresee how their hearts are going to behave, she has displayed a certain amount of mercy within the battlefield, showing something that might be described as respect in front of Shiage's and Rikou's protective behavior while they are faced with danger. Outside combat she seems to act a little frivolous, using her showy appearance to earn extra money.

Battle Royale Arc
She is first seen attacking a car that Shiage, Mugino and Rikou are using to escape, after destroying the car the trio decided to escape all of them used different routes, at that point she sets Shiage as her pursuit target. After a short, clumsy "can't be called a fight" she carelessly let Shiage escape. After that she encounters Shiage again when he is trying to escape with Rikou from ITEM's hideout, in this opportunity the "girl in dress" noted "how kind" Hamazura Shiage was and decided to use her ability to play on his feelings; Kakine was slightly amused that Shiage would go out of his way to "save" Rikou from someone he couldn't hope to win against, and when he was considering what to do the "girl in dress" urged Kakine to just let them go, as they were no longer a threat to their plans, Kakine compelled even though he was worried about Takitsubo Rikou's jamming his abilities at an important time.

Later she informs to Kakine that Mugino Shizuri was taken out due to some infighting within the organization, at that point Kakine noticed that none of the main members were in fighting condition, so the "infighting" only happened with ITEM and their subsidiary organization, at that point the idea of "that level 0" (Shiage) taking out Mugino crossed through their minds, after that she gets the details from what Kakine has discovered about the UNDER_LINE with the Pincet Glove and when he decides to fight it out against the Accelerator she quickly voices her refusal to partake in that battle since she had no insurance of survival.

She has stated that her "source of income" is "scamming" money out of workers, she does this by approaching workers who look lonely, keeping them company, acting friendly and getting them to either spend money on her or outright giving money to her. Kakine pointed out that girls who usually do that get involved in sexual activities, however the "Girl in Dress" stated that she stops before things get down to sex and keeps herself satisfied with whatever money she could scrouge up until that point. The nature of her ability is actually well suited for taking advantage of others such as that, however she didn't disclosed if she used Measure Heart along with her womanly charms on that field.

Volume 19
She is 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 Superintendant Aleister to eliminate Hamazura Shiage, as he was supposed to be dead during the battle royale between the 5 organisations.

Ability
She uses a telepathic class ability of unknown level called Measure Heart (心理定規 (メジャーハート)) which allows her to regulate the distance between people's hearts. Depending on the "distance in the heart" she sets herself to the target will have different reactions, for example in one opportunity she sets her distance to Shiage to the same distance as Takitsubo Rikou's heart was at, at which point Shiage was unable to shoot her, the same way he could not shoot Rikou, despite still objectively knowing that the Girl in the Dress and Takitsubo were two different people. She has noted that depending on the person the result is always different, further pointed out that when having to fight their dearest person, there are some people that feel betrayed and display extreme murderous rage; meaning that she has to be careful on in which level she sets herself when facing a target in order to get beneficial results.

Since her ability isn't used for direct combat, she uses a variety of tools and weapons to attack her targets, such as a mobile cane that can slice metal in half, a ladies gun or a grenade launcher.

Trivia

 * She is the most developed unnamed character in volume 15, furthermore she manages to escape a fateful end when she rejected the possibility of joining in Kakine's fight against the Accelerator.
 * Mugino described her power as troublesome, which left Shiage in awe as he thought that it must be something good in order to get that comment from a level 5.
 * In Japanese fandom, she is usually paired with Kakine Teitoku. This probably comes from the fact that in virtually every appearance that she makes, she is either speaking with Kakine or is standing besides him, even though they don't show a close relationship.

Quotes

 * (To an unknown SCHOOL comrade, most probably Kakine) "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) "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) "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"