Originally Posted by Ilidsor
Before the incident we see in Index episode 19-20, he was just a normal kid (well probably a child error). The horrible experiments/isolation and stuff started happening to him after that.
I think that's wrong. Untill the age of nine he had been studying in the special class being the only student. It was stated that during that time not even scientists could handle him and were scared of him too much due to his uncontrolled powers. Also, children would not rush at him without a reason. If even adults were feared of him, what should we say about children. Also, it never stated that he lived a normal life. Being the child error definitely means that you would not spend your childhood hormally. It is really possible that he was a child error and the fact is that he spent his childhood in the Special Ability Institute untill he was 9 so we can imagine what life he had had during that time. Child errors from special ability institute hadn't got a happy childhood at all. Here is the proof and some lines from the novels:
Vol.5, chapter 1, part 7:
“Oh, that isn't a problem, I don't have classmates anyway.”
“I'm a student in a special class, even though I don't know if it's a good thing or a bad thing,” Accelerator casually said.
Ever since the power development course had caused his ability to awaken, he was drafted into a special class. He was the only one in the class. He didn't need to attend a sports meet, nor did he need to attend a culture festival. Though there were almost two thousand students in his school, the cramped class he attended had only a table.
He had always been isolated in the special class.
Vol.12, chapter 1:
It was on a different scope, but his school had a special classroom. He was the only student in the class and it essentially functioned as a square cage to isolate him as an experimental animal.
Vol.12, chapter 2:
“Just the name of the place you used to be was enough to tell me that.”
“The Special Esper Institute?”
Accelerator easily spoke the name Yomikawa hesitated to voice.
“Its official name is the Special Esper Dual Modification Technology Research Institute. I was forced to live in that school until I was 9. That hell was rumored to have a facility for disposing of corpses on the grounds.”
It was only in Academy City that two mismatched ideas like that of a school and the disposing of corpses would be brought together like that. In that city, schools also functioned as research and testing institutions for psychic powers development. When rumors branched off, the schools could become known as murderous institutions that performed inhuman research.
“But the place was even worse than the rumors suggested. They didn’t dispose of corpses there. It was the opposite. It was a garbage dump for the disposal of living human beings. I’m sure you’ve at least heard the stories.”
“…Yes, I have.”
The Special Esper Institute had focused on experiments and research into Dual Skills. Currently, it had been concluded that students could only use a single power each and that the appearance of two or more powers at once was impossible. Most of the data used to reach that conclusion had been gathered at that institute.
In other words, a long string of failures had led to the discovery of that law.
Psychic powers were developed by directly affecting the structure of the brain using suggestion and drugs. It was best not to imagine what sort of tragedies were created when that failed. Contemplating on that too much could lead you to realize the truth behind the seemingly ridiculous phrase of “a fate worse than death”.
“Towards the end, the Special Esper Institute had to have realized that an esper could only have a single power. Yet they still desired a completed Dual Skill for their own fame, so they sacrificed more and more children. They especially liked to use Child Errors.”
“But unfortunately, I didn’t get to see your heroic actions. As I said before, I was only in the Special Esper Institute until I was 9. I was moved elsewhere then. Do you know why?” The corners of Accelerator’s mouth twisted up. “Because they couldn’t handle me. Even that hell found my power to be too much. Even those demons in lab coats were afraid of me. That’s just the kind of monster I am.” The white student spoke into his cell phone. “And it was no different afterwards. It was all such nonsense. Imaginary Number Institute, the Wisdom Institute, a Kirigaoka affiliate… Well, tragedies are surprisingly soft. That is how I managed to slip through. And when I slipped through, I just sank further. Deeper and deeper.”
And as that monster bounced from place to place with no one able to handle him, he had eventually reached the Level 6 research institution Yoshikawa had belonged to. He had been received exceptionally well there and thus stayed for more than 2 months. But that had only been another face of their fear of Accelerator. The looks on their faces plainly said they were trying not to anger him. The only exception had been that na´ve Yoshikawa.
It seems he had always been the victim of abusing. He was forced to live in the SAI and was surrounded by corrupt adults, researches, not normal people.
Speaking about SAI, toaru wiki also says in addition that he was the only kid who survived cruel experiments during the years spent in that science institute. I hope that helped.
So what is your answer? It seems to me that scene was only his imagination.