A Scientific Urban Detective

Index, true to her name, is also known as the "Index Librorum Prohibitorum" because her mind holds the knowledge of 103,000 magical books.

According to the information provided by Stiyl, 85% of Index's brain has been permanently occupied to store these 103,000 magical books.

That leaves her with only 15% of her memory capacity for daily life.

For someone with "perfect memory," this amount of memory is clearly insufficient because there is no "forgetting" mechanism.

Therefore, to ensure Index's survival and prevent her brain from being overloaded with excessive memory information, the only way, without touching the 103,000 magical books, is to periodically and artificially delete her memory—the 15% related to daily life.

Specifically, this means deleting her memory once a year.

This is why Index doesn't recognize Stiyl and Kanzaki Kaori, even though they are her companions—because her past memories have been erased.

Moreover, the true mission of Stiyl and Kanzaki Kaori's arrival in Academy City is to perform the annual ritual—to erase Index's memories of the past year.

This morning, while Kamijou Touma went out to find a phone to contact Lin Wuming, Stiyl cornered him while he was acting alone. With his injured legs, Kamijou Touma, who could only move slowly with a cane, had no way to escape.

Taking advantage of Kamijou Touma's temporary separation from Index, Stiyl explained the whole truth to him.

Despite his unwillingness, Stiyl ultimately recognized Kamijou Touma's resolve, which is why he chose to confide in him.

However, after hearing that Index would have to have her memory erased in less than a week, Kamijou Touma couldn't accept this outcome.

Although he was intimidated by unfamiliar concepts like "magic" and "magical books," which made Kamijou Touma feel somewhat flustered,

he was, after all, a modern teenager who grew up in a normal society and studied in Academy City; after hearing Stiyl's explanation, Kamijou Touma instinctively felt that something was wrong.

Or rather, he was unwilling.

Kamijou Touma firmly believed that problems that magicians couldn't solve didn't mean scientists couldn't solve them.

Since Index was facing a problem with her brain's memory, Kamijou Touma naturally thought of one of Academy City's Level 5s, the "Mental Out" Tokiwadai queen bee!

Coincidentally, Kamijou Touma was very familiar with Lin Wuming, making it even easier to find Shokuhou Misaki through Lin Wuming.

Hence, the phone call.

Although Stiyl was wary of "Mental Out," he didn't have to worry about Shokuhou Misaki doing anything to Index since it was just a phone conversation, so he tacitly approved the call.

However, to Kamijou Touma's surprise, neither Shokuhou Misaki nor Lin Wuming spoke; instead, Misaka Mikoto was the first to retort.

"What, are you telling a brain teaser?" Misaka Mikoto tried to maintain her image a little, "Uh, Kamijou...senpai?"

"I'm seriously seeking expert guidance, Princess! Hurry up and let the Queen take the call!"

"But the expert is very angry right now," Misaka Mikoto glanced at Shokuhou Misaki beside her.

"Huh? Why?"

"That's why I said it's a brain teaser. Asking an expert with this kind of question will definitely be seen as a prank, right?" Misaka Mikoto said, "One year's worth of memory occupies 15% of the brain's memory capacity. Simple calculation shows that even without the so-called magical books taking up space, 100% capacity can only store 6.6 years of memory."

"But Index is a perfect memory ability user, she doesn't forget any information..."

Misaka Mikoto rolled her eyes: "Perfect memory ability, also known as 'hyperthymesia,' is rare, but not a unique case. A quick search online will show that there are many cases of hyperthymesia patients who live to old age and die peacefully."

"Huh? Oh, right," Kamijou Touma seemed to realize what Misaka Mikoto meant by "brain teaser."

It was a simple elementary school math problem that could reveal the flaw with a simple calculation.

"And after all, the human brain isn't a computer," Shokuhou Misaki finally spoke, "There's no such rigid percentage of capacity...Listen, even if the brain is damaged and only one-tenth of the brain tissue remains, you can still live a normal life and even get a doctorate—there are cases like that. So, forget your ridiculous percentage theory!"

"Huh?" Kamijou Touma exclaimed loudly, "Did you hear that, Flame Magician! You've been deceived! Index can be saved!"

"So, Queen," Kamijou Touma then asked sincerely, "Can you come and take a look? How should we save Index?"

"Since it's not a problem with memory or the brain, there's no point in looking for me, right?" Shokuhou Misaki said, "Besides, the magicians don't seem to want me to touch their forbidden books."

Looking up, he saw Kanzaki Kaori looking over with a complicated expression.

"So...what were we doing before?" Kanzaki Kaori wavered for a moment, but quickly regained her composure, "Sorry, Mr. Lin Wuming, I have to take my leave!"

With that, the female saint picked up her nodachi and left at a speed that ordinary people couldn't comprehend.

The most ⊥ new ⊥ small ⊥ said ⊥ at ⊥ six ⊥ 9 ⊥⊥ book ⊥⊥ bar ⊥⊥ first ⊥ hair!

"Kamijou Touma, how is it over there?" Lin Wuming asked, "Be careful, there's another female magician heading over there."

"Eh? There's another magician?" Kamijou Touma asked in surprise, "But don't worry, the Flame Magician on my side also left suddenly. They should be going to meet up somewhere else, right?"

Feeling that the misunderstanding had been resolved, Kamijou Touma no longer felt hostile towards Stiyl and even optimistically believed that they could become companions.

After all, they shared the same goal—to help and save Index and make her happy.

But soon, the cold reality hit him hard.

"Kamijou Touma, there are less than seven days left until this year's ritual."

Before long, the Flame Magician Stiyl and another beautiful girl with a long sword reappeared in front of Kamijou Touma; then, they threw this cold, hard reality in Kamijou Touma's face.

"Eh?" Kamijou Touma didn't react for a moment.

"In other words, you have a maximum of seven days to try—during this time, Kanzaki and I will no longer interfere with you," Stiyl said, "But if you fail to find a way to save Index, we will still perform the ritual as usual when the time comes."

"What...does this mean? Aren't you going to come up with a solution together?" Kamijou Touma was confused, "You guys are the experts in magic, right? I'm just an amateur. How can I possibly find a way to save Index?"

"That's your problem. Good luck," Stiyl said, "Also, if you try to stop us after seven days, be prepared to be killed."

Without giving Kamijou Touma a chance to respond, the two magicians finished speaking and quickly turned to leave.

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