The next day at U.A. High School was filled with tension and unease. The incident at the USJ had sent shockwaves through the student body, and rumors were spreading like wildfire. The staff was determined to get to the bottom of what had happened.

Principal Nezu gathered the U.A. staff in a somber meeting room, his small, mouse-like face showing a rare expression of concern. "We need to investigate the USJ thoroughly," he declared. "This incident is unprecedented, and we cannot afford to underestimate the threat."

All Might, who should had been at the forefront of the battle the previous day, nodded in agreement. "I'll go back to the USJ and examine the scene. There's no way that monster just vanished into thin air."

Present Mic, flanked by Midnight and Cementoss, spoke up. "We'll join you, All Might. We need to understand how Mr. Tanaka disappeared and what that Thing was."

Nezu turned to All Might, who had been in his weakened form for some time now. "All Might, I know you're not at your full strength, but your experience and insights will be invaluable. Please assist in any way you can."

All Might nodded, determination shining in his eyes. "Of course, Principal. I won't let this incident go unresolved."

As the staff members prepared to investigate the USJ once more, Class 1-A was buzzing with discussion. The students were concerned for their teacher, Mr. Tanaka, and worried about what had transpired. Izuku, in particular, was plagued by thoughts of his missing father and the sinister voice that had echoed in the USJ.

In the meantime, the news of the incident had reached the outside world, and Pro Heroes and government agencies were on high alert. The security around U.A. was tightened, and additional measures were put in place to ensure the safety of the students.

Back at the USJ, the investigative team carefully combed through the area, searching for any clues or remnants of the mysterious creature and Mr. Tanaka. All Might searched in his weaken state, while Cementoss and Present Mic surveyed the damage to the facility.

Hours passed, and despite their thorough investigation, they found no trace of the monster or Mr. Tanaka. It was as if both had vanished without a trace, leaving behind only the unsettling memories of the previous day's events.

All Might finally spoke up, his voice tinged with frustration. "It's like they never existed in the first place. But I heard the recording, and I saw the CCTV. There's something more to this."

Cementoss nodded in agreement. "We need to figure out what we're dealing with. This isn't something we can ignore."

As the staff members left the USJ, their minds were filled with questions and a growing sense of unease. The mystery surrounding the incident deepened, and the students of U.A. High School were left to wonder about the fate of their beloved teacher and the true nature of the malevolent force that had invaded their school.

Little did they know that the answers they sought would lead them down a path filled with danger and revelations beyond their wildest imaginations.

In the days that followed, the investigation into the USJ incident continued, but progress remained frustratingly slow. All Might and the rest of the U.A. staff consulted with experts in Quirk analysis, paranormal phenomena, and dimensional anomalies, but no one could provide a definitive explanation for what had occurred.

Rumors and speculations swirled around the school. Some students whispered that it might have been an elaborate training exercise, while others believed it was an attack by a previously unknown villain organization. The uncertainty weighed heavily on the minds of both students and staff.

Izuku couldn't shake the feeling that his father's presence and that haunting voice were connected to the mysterious events. He spent countless hours researching his father's past and trying to understand any clues that might shed light on the situation. His friends, too, were determined to uncover the truth, supporting him in his quest.

One evening, as the sun set over U.A., the investigative team reconvened in Principal Nezu's office to discuss their findings. Despite their best efforts, they had come up empty-handed.

Cementoss scratched his head in frustration. "It's like the monster and Mr. Tanaka never existed in the first place. No records, no witnesses, nothing."

All Might, leaning against the wall, sighed deeply. "And that voice... it felt personal. Like it was targeting Izuku."

Midnight, who had been quiet for most of the meeting, finally spoke up. "Izuku, have you made any progress in your research regarding your father?"

Izuku nodded, his expression determined. "I've found some old records of my father's work. He was involved in research related to Quirks and dimensional anomalies, but it's all classified. There are mentions of a project called 'The Marker,' but I can't access any details."

Principal Nezu leaned forward, his whiskers twitching in thought. "The Marker..."

The decision was made to initiate a full-scale investigation into the classified records regarding the The Marker project. All Might would use his connections to reach out to his former colleagues in the hero world, while Midnight and the U.A. staff would continue to gather any information they could.

As the days turned into weeks, the mystery surrounding the USJ incident deepened. The students of Class 1-A, led by Izuku, were determined to uncover the truth, even if it meant delving into the dangerous and unknown world of his parents' pasts. Little did they know that their journey would take them to the very heart of a conspiracy that threatened not only U.A. but the entire hero society itself.

The path ahead was fraught with danger, but they had each other, their unwavering resolve, and the indomitable spirit of heroes to guide them through the darkness and into the unknown.

As the investigation into The Marker project continued, Principal Nezu found himself alone in his office one night, poring over his mind. His tiny, intelligent eyes scanned the city, searching his mind.

Suddenly, the room grew colder, and a shiver ran down his spine. Nezu looked around, his keen senses on high alert. That's when he heard it—the same haunting voice that had echoed in the USJ.

"Rat," it whispered, sending a chill through the air. "You're getting too close. Stop digging into the past, or you'll regret it."

Nezu's fur bristled with unease, but his determination remained unshaken. "Hisashi, what do you want?" he demanded, his voice unwavering.

The voice didn't respond, but the threat hung in the air, and then it was gone, leaving the principal with a lingering sense of foreboding.

Meanwhile, Izuku had been tirelessly researching The Marker project, delving deeper into the classified files he had managed to access. His room was filled with notes and diagrams, a testament to his relentless pursuit of the truth.

One evening, as he sat at his desk, lost in thought, his mother, appeared in the doorway. Her eyes were tired and filled with worry, but there was a determination in her gaze.

"Izuku," she said softly, stepping into the room. "I know you're trying to find your father, but you need to stop."

Izuku looked up, surprised by his mother's sudden visit. "Mom, I have to find out what happened to him. I need to know."

Inko's voice trembled with emotion. "Izuku, I understand your pain, but there are things you don't know. Your father... he was involved in dangerous research, and it led to his disappearance. The past should stay buried."

Izuku was torn between his desire to reunite with his father and his mother's plea for caution. "But Mom, I can't just ignore it. I have to uncover the truth."

Inko reached out and placed a gentle hand on her son's shoulder. "Izuku, please. Your safety is more important to me than anything else. Promise me you'll be careful."

Izuku nodded, his resolve unwavering. "I promise, Mom. But I can't give up on this. Not now."

Inko sighed, her maternal instincts warring with her son's determination. "Just promise me you'll be cautious and lean on your friends for support. You're not alone in this."

Izuku smiled warmly, touched by his mother's concern. "I will, Mom. And I'll make sure we all come through this together."

As the days passed, the investigation into The Marker project intensified, and the haunting warning received by Principal Nezu served as a stark reminder that the mystery surrounding the USJ incident was far from over. The students of Class 1-A were about to embark on a perilous journey that would test their bonds, their strength, and their resolve as they pursued the truth hidden in the shadows of their parents' pasts.

AN: If you know the reference I used, you have a idea on what i am somewhat going for, along with some other things.