Class 1-A Radiates Chaos

Shouto's Big Break

Who's the killer? Well, no other than the UA cryptid himself, Shinsou Hitoshi.

Many things lead him to this conclusion, but the first big hint had been when he'd overheard Shinsou speaking in the cafeteria about his 'Zodiac'. Shoto was immediately intrigued and had googled it to figure out when exactly it was. He'd been horrified to find something about a cryptic serial killer from many years ago, but the real question was, "Why does Shinsou know so much about them?".

From there Shouto began digging, and what he found would shock and horrify him for years.

The first thing he noticed (when stalking Shinsou) was his unusual and nearly sporadic behavioural patterns. He was up late at night, would constantly switch between dorm buildings, climbed through vents, and he did it all with a bored and, dare he say, sociopathic look on his face. He consistently staled different UA dorms and left with different objects and brought them to the woods by UA, it was almost as if he was planning something... something devious .

It had taken all of Shouto's courage to bring himself to dig further into it as he started to realize more and more killer like things about Shinsou.

He was clearly a sadist, he laughed as Katsuki chased Izuku around threatening him with death. Only a killer finds death threats funny.

He had seen Shinsou drink something red in the cafeteria one time. He was certain it was blood.

Shinsou consistently wanted to die. Who else would want to die other than an immortal being who had been alive for hundreds of years?

Shinsou was also fluent in English and used riddles to activate his quirk a lot. It was almost as if speaking in codes was nothing foreign to him.

But the real nail in the coffin had been when Shouto had directly asked if Shinsou was an immortal serial killer who was known for leaving hidden messages with his victims.

Shinsou had smiled and replied, "Wouldn't you like to know, Weather Boy?"

Shoto had rushed home to find out what 'weather boy' meant. He knew the Zodiac killer was known for being hard to decode so he gave it his all.

He concluded that he was asking "Weather or not he wanted to live".

Shoto felt a chill go down his spine. It all went downhill from there.

The next day he walked into class and saw the ceiling vent hanging open above his desk with a picture of an angry cat taped to it. He was being threatened.

Then Shinsou began following him everywhere he went, but whenever he'd try to turn around and catch him all he'd find was a small slip of paper with a jumble of shapes and letters on it.

Then he'd seen Shinsou carrying a large trash bag across the UA campus, Shinsou had just looked him in the eye, then winked. Shouto was petrified.

But the final straw was when he went to report his findings to the principal. He had walked into the principal's office and approached the desk, only for the large chair to turn around and reveal none other than Shinsou Hitoshi.

He had turned to Shouto with a large grin, brandished a stuffed animal that looked alarmingly like Nezu, and asked if he needed something. Shouto was shaking with fear.

Then Shinsou stood up, set the rat doll down, and stabbed a knife into the doll.

"Shit, my knife slipped," Shinsou had gasped innocently.

Then a loud squeak erupted through the room, "Help help!".

Shouto gasped loudly, Shinsou had just attempted murder right in front of his eyes.

So, he was forced to break character for a moment. He screamed at the top of his lungs, socked Shinsou in the face, and ran for his god damn life as Shinsou cackled.

His principal was dead and he was the Zodiac Killers next target. The life of crime-solving is cruel.

(He passed out the next morning when Nezu rode into school on Shinsou shoulder).

~~ DadMight ~~

Now, the first time Shouto had ever discovered something that was a threat to national security was the case of Midoriya and All Might. This theory had come about during the sports festival when he noticed alarming similarities between the two.

The first thing he had noticed was the first day when Izuku had showcased amazing strength. He had looked exactly like All Might. From the force used to throw the ball, to the smile on his face. It just screamed 'I'm related to All Might'.

But that theory was encouraged more and more as All Might and Izuku had multiple private meetings and All Might made it clear that they were related in some way.

Shouto was ashamed to admit that, in a moment of weakness, he thought All Might may be some form of sugar daddy. He did not believe that now.

But he had been absolutely certain that Izuku was All Might's son. They acted so similarly. But Izuku had shot him down when he asked.

So, Shouto went back to the drawing board. They had to be connected somehow.

Shouto spent weeks trying to decipher the mystery. Between how much Izuku's quirk was evolving and how clearly he mimicked All Might, it was impossible to prove him wrong.

So, he did the smart thing.

He paid Recovery Girl to take blood tests from both of them and tell him if they were related.

The results? Negative. Shouto was flabbergasted.

Until, of course, Kamino happened. This brought new information to light.

There was a villain that could take and give quirks, but All Might had deflated completely. There's something else at work here.

Maybe it's not the personality All Might passed on, but his quirk.

If there's a quirk that could steal others, is it possible that All Might's quirk gave him the ability to pass his on? Is that why Izuku struggled to contain it? Did it just build so much energy that Izuku's body couldn't handle it?

Was Izuku All Might's true successor?!

. . .

Nah. That's too crazy. Even for Shouto, that's a bit out there.

Shouto sighed, "Back to the drawing board, I guess,".

~~
Three all-nighters later and Shouto had found the truth.

Kaminari's mom had an affair with the villain Muscular, so Izuku was forced to hide his true identity. Shouto had no choice but to help his friend in these trying times.

I only had this idea because the concept of Shinsou scary the hell out of Shouto makes me laugh a lot