After creating the scene of his own death, Noah used the magic door to arrive on the outskirts of the village before closing his eyes and mobilizing his mana.
Inside his mind, different universes manifested as an infinite starry sky, where each star represented a different universe. Despite appearing infinite, if one were to count each of these stars, they would find between 9,000 and 10,000 in total.
As long as he concentrated, a mysterious force would guide him to the universe he desired, causing the star representing that universe to light up.
But to cross the barrier between realities, Noah couldn't rely solely on his own power.
He released a large amount of mana from his magical core, channeling it in a precise yet instinctive process. This mana wasn't used directly for traveling; rather, it acted as a catalyst to attract void energy, a primordial force that existed beyond time and space. The more mana he released, the more void energy responded to his call, swirling around him like a sea of pure potential.
Once he had gathered enough energy, the formation of the dimensional tunnel began. The void energy compressed and spun violently, forming a spiraling vortex that extended toward the star Noah had unconsciously selected as his destination. The key to traveling wasn't moving through conventional space but piercing the cosmic wall of the target universe.
However, not all universes could be penetrated easily. Each was wrapped in its own quantum membrane, a conceptual barrier that protected its existence from the chaos of the void. Universes with stronger cosmic walls required a more intense dimensional tunnel, meaning exorbitant amounts of mana had to be spent to attract enough void energy. Because of this, Noah was restricted to traveling only to low-level universes or purely technological ones without any supernatural aspects, whose walls were weak enough to be breached with a lower-powered tunnel.
Despite all the phenomena occurring around him, Noah was completely unaware of them.
To him, he simply thought of a world he wanted to travel to and instinctively released a certain amount of mana from his core.
As long as he entered the spatial vortex, he would immediately appear in the universe he desired.
When the vortex reached its peak stability, Noah was absorbed into it, launched through the distortion of space-time. His perception of his surroundings vanished in an instant; he felt and saw nothing as his body was transported beyond reality itself. Only when the tunnel completed its trajectory and crashed into the atmosphere of the new world did Noah regain consciousness.
Looking around, he found himself in the middle of a dark alley.
Stepping out of the alley, he stood on an unfamiliar street, surrounded by tall buildings and flickering lights.
His shinobi attire and the ninja gear he carried made him stand out too much among the crowd of passersby dressed in Western-style clothing. It didn't take long for him to notice several curious glances directed at him.
"Alright, first thing's first… blend in," he thought.
After searching for a moment, he located a man of similar build to himself exiting an alley.
In the blink of an eye, Noah slipped behind him. A precise strike to the nape, and the man fell unconscious without making a sound. Minutes later, Noah emerged from the alley in new clothes, his hair concealed under a hood.
Taking out the magic door, he opened it and teleported to an unknown location.
Fortunately, the topographic map registered in the door was still functional since both Doraemon's world and this world were based on Earth.
Only a few places in this world were currently beyond the reach of the magic door.
A while after he left, a group of people with wands in their hands arrived at the location to inspect the area, but they found nothing.
Meanwhile, Noah appeared in the middle of an ordinary mountain in Tibet.
Using Earth-style jutsu, he began creating a hole.
When he had dug over thirty meters deep and felt that the earth had become much harder to mold with his chakra, he began expanding the walls around him.
When he was finished, he started taking out the various machines he had stored in his 4D pocket.
Finally, he connected the machines to a power generator, and his new secret laboratory began operating.
At night, he sat cross-legged and started casting a fuinjutsu.
Sealing patterns began to wrap around his mana core, and the chakra in his body decreased from the level of a Jonin to that of a villager with almost no chakra.
His magical power also decreased to match the level of the young wizards in this world.
After all, with his magical ability, he could perfectly cast any spell from this world without needing a wand.
The next morning, he used the magic door to arrive at King's Cross Station. There, among the families bidding farewell to their children, he spotted a boy about his age pushing a cart with various items.
Without making a sound, Noah formed a hand seal.
"Henge no Jutsu," he whispered.
In an instant, his appearance changed, adopting the boy's looks. Before anyone noticed the difference, he led the boy to a secluded corner, knocked him unconscious with a precise strike, and dragged him into the magic door.
In his laboratory, he placed him inside a suspended animation chamber before returning.
Noah still had a final goal, and he wouldn't kill an innocent little boy who had done nothing to him just because he wanted to take his place.
Noah stopped in front of the barrier between platforms nine and ten. Looking around, he saw several children with their families disappearing through the brick wall.
Without hesitation, he did the same.
On the other side, the Hogwarts Express awaited, its red locomotive steaming, with dozens of excited students boarding the carriages.
Noah blended in among them. He was already used to acting like a child, and his ninja training allowed him to adapt quickly.
He boarded the train and found an empty compartment. Closing the door, he took out the letter he had taken from the boy.
"Let's see who I am now…"
He opened the envelope and read the name on the letter: Theodore "Theo" Campbell.
As he pondered his next move, the compartment door slid open, and a girl with bushy brown hair peeked inside.
"Can I sit here? All the other compartments are full."
Noah hesitated for a second before nodding.
"Go ahead."
The girl entered and sat across from him.
"I'm Hermione Granger. And you?"
"Theo Campbell."
Noah was slightly surprised to see Hermione. Unlike the Hermione from the movies, played by the beautiful Emma Watson, the Hermione in front of him could be called unattractive at best.
This was Hermione just as she was described in the books.
Hermione smiled and pulled a book from her bag.
"Nice to meet you, Theo. Are you excited about Hogwarts?"
Noah smiled calmly.
"Yeah… it should be interesting."
As the Hogwarts Express moved forward, Noah—or rather, Theo Campbell—watched Hermione closely. Her enthusiasm for magic was evident; she talked non-stop about the books she had read and how excited she was to learn spells.
"And you?" she suddenly asked. "Are you from a magical or Muggle family?"
Noah blinked. He wasn't sure how to answer. Luckily, the boy he had replaced was probably a Muggle-born, as he didn't recall a Campbell family among the magical ones.
"My parents are Muggles. All of this is new to me."
Hermione smiled excitedly.
"Same here! I've read everything I could about magic, but knowing it in theory is different from seeing it in reality. Imagine actually casting spells!
Did you know Hogwarts is over a thousand years old? And that there are four houses: Gryffindor, Hufflepuff, Ravenclaw, and Slytherin? Which one do you think you'll be in?"
Noah shrugged.
"I don't know."
Hermione seemed ready to launch into another explanation when the compartment door opened again. This time, two boys entered: one red-haired, freckled, and wearing worn-out clothes, and the other with glasses and a lightning-shaped scar on his forehead.
"Can we sit here? There are no more free seats," the redhead asked.
"Sure," Hermione replied before Noah could say anything.
The two boys sat down.
"I'm Ron Weasley," the redhead said, pulling out a sandwich from his robe.
"And I'm Harry Potter," said the boy with glasses.
Noah noticed that Ron was looking at Harry with a certain admiration. Hermione, on the other hand, widened her eyes.
"Are you the Harry Potter? I've read about you in A History of Magic!"
Harry looked uncomfortable.
"Oh, really?"
"Yes! You're famous in the wizarding world. You defeated... well, you-know-who, when you were just a baby."
The journey continued with conversations about Hogwarts, the houses, and basic spells.