Four girls were in a hospital.
The area they were in was not off limits, but people almost never came there because of how far away it was from the routes leading to the exits. In the hospital, it was known as the clinical research area, but warm sunbeams came in through the window despite that over-the-top name.
The girls were standing in the hallway.
All four of them had shoulder-length brown hair and skin so white it almost looked transparent. They all had the exact same silhouette and their eyes were the same in every way from the shape and color to the iris and retina. Despite the season, they all wore the Tokiwadai Middle School summer uniform: gray pleated skirt, short-sleeve white blouse, and sleeveless summer sweater.
They went by many different names.
The Sisters.
Radio Noise.
Mass-produced military models of a Level 5.
Due to the effects of growth acceleration techniques using genetic manipulation and drugs, their lifespan had been drastically reduced. They were undergoing various treatments in the hospital to overcome that, and they were going to begin the second stage of that treatment today.
They had lived in the hospital up to that point, but they would now be heading outside bit by bit for rehabilitation.
A doctor with a frog-like face spoke to those Sisters.
He was holding a small clipboard of the sort waiters used.
"Are all of you okay with wearing Tokiwadai Middle School's winter uniform while outside?"
"That is not a problem, replies Misaka #10032," said one of the four girls.
They could only be distinguished by serial number rather than by name. That frog-faced doctor had not decided on that. It had apparently been a decision from when they were being produced.
"Is the same size fine for all four of you?" said the doctor as he wrote their "order" on the clipboard.
In response to his question, the four Sisters did not even exchange a single glance. Their expression made it clear they felt that was a silly question.
"There is no need to even take measurements. We all match, answers Misaka #10032."
"Every Misaka was made from the same genetic information. We are mass-produced models, adds Misaka #13577."
"Since we were all made via the same process, there is no need to even entertain the possibility of differences, concludes Misaka #10039."
"M-Misaka is…"
The final girl trailed off.
"…?"
"…?"
"…?"
The other three Sisters turned toward the one that had made that inarticulate comment, and Serial Number 19090 averted her gaze and shrunk down. From the way she used her hands, it seemed she was trying to hide her upper body.
#10032, the girl a certain boy referred to as Misaka Imouto, looked over with a bit of suspicion in her eyes. She then approached #19090 as if she had just realized something.
She clenched both fists with just the thumbs extended, turned those fists upside down, and stuck her thumbs into the gap between #19090's body and skirt.
"Mh!? According to the spec sheet, we should all be exactly the same, but there is enough room for two thumbs, says Misaka #10032 in an emergency report!!"
"But every Misaka should be the same, says Misaka #13577 as she displays her shock!"
"Her waist may be different but what about the rest of her? says Misaka #10039 as she completely calmly suggests a thorough examination."
To carry out that plan, #10032 pulled her thumbs out from the skirt and moved them upwards, but #19090 used both hands to intercept them. Unlike the other models, her face was tinged a bit red and her facial expressions seemed more diverse.
With a shocked look on his face, the frog-faced doctor said, "The faces and physiques of monozygotic twins can grow distinct due to differences in diet and exercise, so maybe this is the same. It wouldn't be surprising to see variations in style between clones."
The doctor silently regretted some things he had said before.
This situation had come about because he had taught them that skinnier girls were better, and the better the girl, the more choice they had in guys. That was simply the frog-faced doctor's own prejudiced preferences, but the Sisters knew very, very few guys. For that reason, they assumed that the frog-faced doctor was a good example of an average guy and had likely come to the conclusion of "If this man thinks that, then perhaps that high school boy thinks so too, decides Misaka amidst her confused thoughts".
And he did not know where the knowledge had come from, but they had also learned that there was a special ring that was placed on the ring finger and that a girl had to be the best she could be to acquire it. He was not sure whether to call that information accurate or not, but it had led the Sisters to grow more and more individualistic nonetheless. (Although the Sisters themselves did not seem aware of it.)
"So this Misaka has been going behind the other Misakas' backs and cheating with a diet, says Misaka #10032 as she continues the investigation."
"#20001 aka Last Order is supposed to keep control of every Misaka. What is she doing? asks Misaka #13577 as she brings up the concepts of mission and duty."
"She is so little that she may not know what the purpose of those actions was, speculates Misaka #10039 as she keeps a level head."
While the Sisters spoke back and forth, the frog-faced doctor spoke up once more.
"Is this really something to get that worked up over? You are all the same basic model, so can't you achieve the same result by doing what #19090 did?"
"…!!"
"…!!"
"…!!"
Three of the Sisters turned toward the remaining one at high speed.
#19090, the Sister who had acquired a weight-loss technique before the others, slowly stepped backwards.
"Misaka will do what her danger management ability tells her and run away! says Misaka as-…!!"
Before she could finish shouting, the other girls jumped at her.