In Mikado City, home to 280,000 people, a Gate to another world opened one fateful day. Invaders from another dimension known as Neighbours poured through.

The city then knew true fear.

Atsuko can remember that fateful day as if it was just yesterday. It was a Sunday, and it began like any other. Papa was home from his business trip, and Mama had already left to take care of the bakery. She was only 10 at the time, but she had chosen to take care of her twin brothers, who had only begun to toddle on their own.

Papa had allowed them to go out to the nearby park with a handful of pocket change for any snacks. Their neighbourhood was quiet despite its proximity to the shopping district, but it was safe. He knew his daughter was responsible enough to take care of the twin devils by herself, so he didn't worry about them going off on their own. The only order he gave her was to head over the bakery once they were done to pick up Mama and some goods for dessert.

Papa knew Mama would never give him his favourite apple crumble if he asked her himself.

The siblings had spent a few hours at the playground before the twins, Hikaru and Haruki, had begun to doze off. Placing them in the wagon and securing them, Atsuko began pulling them towards the bakery. They were only a few blocks away when a flash of black lighting suddenly hit the city. The young girl stumbled on her feet, moving to hover over her now crying brothers, staring warily at the growing magma of black energy. Her dark eyes widened, breathe hitching as monstrous forms began wondering out of the portal.

Atsuko didn't know what was wrong, but suddenly she couldn't move. She couldn't breathe. Her body would not listen to her. It was the desperate cries of her brothers that unfroze her.

It was chaos. Everyone was screaming and running away from the sudden alien invasion. Atsuko gained bruises and scraps on her hands and knees, and people trampled over each other to get to safety. The wagon would only slow them down, so Atsuko had grabbed the twins and, with the aid of the adrenaline pumping in her, carried them to the bakery. Seeing her mother's blonde hair, identical eyes held relief before fear filled them.

She tripped backwards as one of the monsters suddenly appeared from the alley, and two others came from either side of the street.

She shut her eyes, ignoring the screams, ignoring the throbbing pain in her heart as it numbed, and curled over her brothers.

Many thought the fall of the city was inevitable, but then...

It was the sound of something crashing that allowed Atsuko to open her eyes. She gasped, seeing that the monster was down, a man in a blue jacket and a glowing sword standing victoriously above him. From the buildings above, another man in a black trench coat dropped down beside us, lending out a hand.

She grabbed it warily, allowing him to help her up, eyes trailing to geometrical crest on his coat.

A mysterious group drove off the invaders and delivered a message.

"Leave the Neighbours to us. We have long trained for this."

"Where are your parents, little one?" The man questioned, searching for anyone with similar looks to the little blonde girl in the vicinity.

"Papa's at home. Mama's at the bakery."

Atsuko whimpered slightly as the adrenaline began to wear off and the stinging pain of her injuries set in. Holding in the tears as she looked over behind the man where she could see a fallen form, lying helplessly on the ground, a pool of red growing beneath her.

The man frowned, looking over his shoulder towards the closest bakery. His heart dropped when he caught sight of the destruction and the similar coloured locks of the fallen woman. Kneeling down, he placed his hands on her shoulders.

"Kid, I need you to listen to me. It's dangerous. Go find somewhere safe." Taking her hand, he placed a circular object in it. "This will let me find you when we are done here. Now go, and keep your brothers safe."

She stared into his dark eyes, searching for any signs of deception. But deep in her heart, she knew this man was one to trust. That he will protect them from the invaders. Her heart warmed, and the man blinked as if noticing something out of the norm. Before he could question her, she nodded and ran off with her brothers in her arms.

They studied Neighbour technology and created an organization to defend the world against them.

Atsuko had found a collapsed building that hid the doors to a basement bunker that was probably used to store food. Shutting the door, she ignored the darkness and held her brothers to her, letting them rest from the trauma they just experienced. It wasn't long until the city became quiet. She froze as the door swung open. She blinked to get used to the light once more and smiled tiredly at the familiar man.

He nodded when his eyes met hers and held out his hand. Unlike last time, Atsuko didn't hesitate to place her small hand in his.

[ The Border Defence Agency ]

Though filled with grief about the news on his wife, Papa was grateful that his precious children were safe. It wasn't long after that fateful day that the group built a tremendous base in a short time.

Four years later...

"Papa! I'll be going now!"

"Be safe! Remember, you have a shift at the bakery around six and to pick up your brothers at kindergarten!"

"Hai~."

Slipping on her shoes, the now young teen bounded outside, taking her usual path to school. She grinned when she caught sight of the familiar back of her friend.

"Osamu-kun! Wait up ~."

The magane boy blinked, snapped out of his dazed admiration of the border headquarters, nodding in greeting to his friend.

"Ah, Atsuko, running late again this morning?" He wondered, seeing the somewhat dishevelled state of her uniform.

Atsuko smiled sheepishly as she went about fixing her uniform. Osamu assisted her by carrying her bag as they continued on their way to school.

Though the Gate is still open, and the Neighbors still come through, most of the city's population has chosen to remain. Perhaps due to their faith in Border, the regular explosions and flashes hardly even faze the people living in Mikado City.

"I'll meet up with you in class later! Mizunuma-sensei asked me to meet with her at the faculty office." Atsuko smiled, waving at her friend before jogging off. Osamu waved back curtly as he slipped on his own indoor shoes before shutting his locker.

Humming under her breathe, Atsuko smiled and greeted everyone that passed, receiving smilier greetings in turn. Knocking on the faculty office doors, she slid the door open, peeking her head through.

"Good morning, sensei! Is Mizunuma-sensei here?" She greeted, bowing politely as she entered.

Seeing the blonde, Mizunuma smiled, waving her student over as she finished organizing the files for today's class.

"Good morning Mizutani-san. I asked you to come here so you could meet the new student and guide them as you're the class president, but..."

"No one is answering the phone," One of the other sensei sighed, rubbing his head, "Late on his first day? This kid is going to be trouble."

Atsuko blinked, nodding her head in understanding. "When they do show up, I don't mind showing them around and explaining the school's rules and protocols, sensei."

Her homeroom teacher smiled, bowing her head gratefully. "Thank you, Mizutani-san. Now head off to class. I'll follow after soon enough."

Bowing, she made her way out and bounded off to the classroom. Hopefully, there'd be enough time for her to complain to Osamu about her brothers' pranks again.

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[ d ^ 3 ^ b ]

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Osamu winced when something hit his head from behind. He frowned at the pencil case, glancing over his shoulder at the three students who always caused trouble.

"Haha, oops!"

"Learn how to catch!"

"Give it back, guys!"

"Hey, four-eyes, give that here."

Osamu took a breath and grabbed the case. As he made his way passed the trio, he must have looked quite intimidating as they stepped away slightly as if expecting him to fight back. Placing the pencil case back in the owner's hands, he nodded at the thanks he was given.

One of the trouble makers whistled at the Megane boy's usually cold reception.

"He's so cool."

"We'll get frostbite."

The students had already found their seats when they noticed their sensei was running late.

"Is the exchange student coming today?"

"Ah, that's why the teacher is late."

"Weird that someone would come here."

"Yeah, into a war zone."

"What if it's a Border agent?"

"Ne, Mikumo-kun, is Mizutani-chan running late again?"

He blinked as one of his female classmates snapped him from his thoughts. Glancing at the clock, he shook his head.

"Mizumuna-sensei asked to meet with her before class."

"Oh! Sensei must have asked her to lead the student around today!"

"That's Kaichou for you, always so reliable."

Speak of the devil, and he shall appear. Osamu thought when he caught sight of long blonde hair entering the room.

"Good morning, everyone!" Atsuko smiled brightly.

Many greeted her the same, some moving to ask about the new student.

Atsuko laughed, waving her hands for everyone to calm down. "Ma ma~ They're running late today, but we'll all have the chance to meet them soon. Now everyone, return to your seats. Mizumuna-sensei said she wouldn't be far behind me."

Like always, everyone followed her orders but continued their conversations with their friends.

"Late on his first day?"

"He must be the bad boy type!"

"No way, maybe he just got lost. He is new to the city after all."

Despite all the theories, the student did not appear as they expected.

"My name is Yuma Kuga."

Atsuko tilted her head curiously as she stared at red eyes and white hair. 'Albinism?' Her back straightened as a sense of loss overcome her, along with a faint touch of playfulness. 'This boy...'

"I'm short, but I'm really 15. Please excuse my tardiness."

Atsuko hid her giggled behind her hand at the clumsy pronunciation and introduction, eyes soft and understanding.

'I think we'll be great friends.'

- - - - - - - - - -

A/N I know. Another fanfic? You already have others you need to update. I know. I really do. But... World Trigger needs more fanfic and thus, this came to be. Updates will be sporadic. Probably only when I feel inspired to do so. But meh, I write fanfic for me tbh. I am god in my fanfics. What I say goes lol.

Updated: 20/02/29