Hello, fellow readers! It's been quite a long time since I developed a fic on this site, and admittedly, I should've been more committed to my other story, which is definitely not dead, but other distractions in life happened. Now, recently I watched and finished the Hunter X Hunter 2011 anime series which quickly became one of my top series to watch. Killua being my favorite from the franchise.

I had been thinking of writing a story for this beautiful series for a long time, and I was scrolling through this site and realized that people had yet to write a story of HxH crossed over with DC. I thought it would've been interesting to see both franchises crossing over, I think they could mold pretty well, considering both have similar tones. I thought up an idea inspired by other crossover fics, and here we are with this story. Now, this DC Universe where Killua is trapped will have elements I have borrowed from multiple DC media such as the comics (Mainly Post-Crisis and Rebirth), movies, animated series (DCAU), and games (Arkhamverse).

Disclaimer: Characters in this story belong to Yoshihiro Togashi and DC, respectively.

This chapter has been edited.

Chapter One:

Lost X In The X Unknown

Killua sat in a fetal position as he leaned against the apartment window. His sharp ocean-blue eyes roamed across the vast scenery of the downtown skylines of the city. The sky alone showed signs of the sun ascending through the horizon that was enveloped by the towering structures of the city. The boy sighed grimly.

This marked the third day since he had found himself stranded in this town with no clear evidence of arriving there physically and consciously. Admittedly, he had remained dazed and sat still frivolously in this unused room of this apartment he had infiltrated in this entire period; he just couldn't process the recent series of events that transpired.

He had no time for that. This situation at hand was the priority that had been a thorn in his side the entire time.

He made various attempts to use his phone, but for some twisted reason, it couldn't detect any compatible signal. He tried contacting Gon, Kurapika, Leorio, or anybody, but to no avail. It was like he was not even in the world anymore.

In fact, this city shouldn't even exist, he initially thought he wound up back in York New City, but he had no recognition of the skylines. Was he in a country that he never knew? But that was impossible. When he trained as an assassin, he was required to know and study the entire map of the known world, so that couldn't be it. The letterings he would see on every surface were impossible to decipher. He recognized the language. It was much more uncommon than the universal tongue that was heavily relied on. Still, regretfully he had never made any effort to teach it to himself.

Killua sighed once more. It would be a struggle to locate a library, not to mention to communicate with the locals. His already dreary spirit sunk further as the thought came to mind; he was alone. Alluka wasn't with him. He missed Gon terribly, as it had been an entire year since he parted ways with his best friend. Kurapika and Leorio came to mind as well, he might not have been as close to them as to Gon, but if they were to step through the room door, he'd jump up in joy. Killua clasped his hands tighter against his knees, his face was nonchalant, but it was clear it upheld melancholy. He could feel the dam behind his eyes threatening to leak, but he was having none of that.

Killua slanted his eyes. He knew his friends were fine as they pursued their goals. But his sister was the one he was worried about most, "Alluka..."

He remembered exactly what had happened before he found himself in this city. Illumi, his brother, had finally found them after a whole year of traveling the world with Alluka. He and she had gone to many places, taking in many beautiful sceneries of the world and cityscapes during that period, all while avoiding the Zoldyck influence.

Illumi had cornered them, reminded him that he could not escape his destiny, and let him know of the very large power gap that Killua had yet to close. Killua's muscles tensed at the memory, even after going through so much in his time with Gon in the pursuit of his father, he still had yet to reach a level to rival Illumi. Before Killua would fight back against his wicked brother, Nanika decided to come out, and Killua couldn't think of a worse time to do that. Then, she made a sacrifice and used her powers to send him to a safe place, far enough to avoid Illumi's wrath.

Killua shook his head at those reasons. Even after days, he still couldn't process that action she had made. Was it an impulse? It had to be if they had time for any rational decision, he would've convinced her that he would stall Illumi long enough, and maybe he could've helped her escape to Whale Island.

Hardening his face, Killua couldn't allow himself to sink further. He turned his face wholly to the window beside him; he didn't know where this place was. His days of quietly drowning himself in sorrow had passed. He had to act if he desired to see the world that he knew. Alluka was in danger. He didn't know what Illumi had in plan for his sister.

If Illumi had harmed one strand of hair on her body, Killua would hunt him down until the end of the world and kill him himself. Fueled by his fury for his brother that burned through his veins, Killua stood up abruptly and turned his entire body towards the window. If he allowed himself to explore and gather information about this place, he would have to learn the language himself. It would all be worth it if saving Alluka was the end goal.

After bursting through the window, Killua stepped onto the apartment balcony. The chilling morning wind fanned his being, and the sleeves of his blue turtleneck and white t-shirt played along with the breeze as his silver hair quivered against the rush. Killua leaped up to the gabled roof and looked out momentarily before bounding from roof to roof.

He took several side glances down at the public rush of the streets and noted that everything about this city was very similar to York New. The many businesses on every corner, the traffic of vehicles on the main roads, and the crowds of pedestrians on the sidewalks. At least the daily city life retained its usual nature.

Killua picked up his pace at amazing speeds. He had no desire to waste any time for Alluka's sake. He had to make a good guess to locate a library to learn this language and use their computers for research.

After a long time, Killua looked up, and the sun was already closing toward the sky's peak. The morning was about to end. And he still couldn't find this library; he was sure he had only traveled at least half of this city. The section of the town he was currently at was near a coastline of a great body of water. Far off the shore was an island with a bridge extending towards the mainland.

What Killua found odd about the piece of land was a built-in mansion with a tower that stretched upwards, ending with a pointed roof. Was that some sort of prison? He would find out about that later. The public library was his main priority. He looked down from the rooftop, surveying the entire block down below. Killua groaned. All these places looked the same from his perspective. He clenched his fist, and anxiety began to tense through his muscles. He might have to get down to where the crowd was. Something he had been hesitant with. Considering his rather pale appearance than the residents, he'd be a sore thumb in the crowd.

At least on this street, it was less crowded than the city's main parts. Killua held his breath before steadily releasing it, "For Alluka." As he neared the roof's edge, he made sure that there would be an obscured area from the public street. He didn't want to draw the attention of the civilians. He stepped off the multistory building and allowed gravity to do its job. Any lesser person would've fallen to their death with their frail body would get crushed against the hard, dense concrete surface.

Killua landed gracefully from the fall and took a neutral stature. He placed his hands in the pockets of his baggy shorts and took a nonchalant stride through the alley. Killua looked forward and saw that the route would lead him to take a sharp turn to a narrow way that led toward the street. Killua took the turn and slightly narrowed his eyes. Just waiting near the exit to the public open were a trio of men with their backs leaned against the brick exterior beside each other.

One of them lit a cigar in his mouth with a lighter before he puffed out the smoke. His partners had their arms crossed with their eyes closed as if they were waiting for something, like an opportunity.

Killua snorted to himself, he may be quite young, but they were no threat to him. So he continued forward. He retained his neutral facade. It'd be their fault if they decided to provoke him.

The man with the cigar looked up once the boy entered his field of vision and smirked. He nudged his elbow to the man to get his attention. He motioned his head to the newcomer, and the last group member caught on.

The first thug studied his gaze at the boy. The fact his skin was pale, along with his hair, was quite odd. Nonetheless, "Hey, kid! You lost?" The thug with the cigar called out.

Killua darted his sharp eyes toward him momentarily before continuing. The thug blinked at the kid's indifference; generally, kids tend to squirm when approached by a stranger. That made them easy targets. This must be one of those street kids that would act all tough and proud that he's one of the tough kids. Smirking, he wanted to see if that kid could keep his tough act when they would take him as a hostage to rob a store nearby.

"Hey!" He stood away from the wall and slowly approached the boy. "I'm talking to you!" The other cronies followed closely. Killua sighed and ceased his steps, and craned his neck towards them, his face filled with boredom.

Once the three gathered up to the boy, the thug beside the first one took his turn to take a crack at him. "What's a boy like you doing all by yourself in these parts? Lost your way to your mother?" The second thug snickered.

The taunt didn't seem to falter the boy, and he didn't even look at them; he stared ahead towards the space behind them as if that had caught his interest than a group of men that decided to corner him. Each thug lifted an eyebrow. Was this kid mental? Any other boy his age should already be cowering, begging them to let them go.

Something wasn't right about this boy, the atmosphere around him and that look in his eyes made them somewhat uneasy. The third thug growled. This was just a stupid kid; he must be from Arkham if this was his attitude. What could he do to them?

"That's it," He pulled a knife from his pockets and wielded it threateningly towards the boy, "Enough with the chit chat. You're coming with us, or you'll have your throat slit. Your choice."

Killua didn't understand a word these morons had said to him. He could feel their hostility growing with each second that passed; he knew that much. But what were they going to do? He glanced at the knife with indifference before he closed his eyes and slightly dipped his head, "Baka…."

The thug flinched slightly at the foreign word the boy uttered, "W-wha-?" Suddenly, the boy vanished, and then the man felt a stabbing pain at the nape of his neck before blacking out. The others didn't react until their partner's body hit the concrete. They turned to their fallen mate in shock.

"Where'd the kid go?" The thug in the middle was smacked sideways to the head. He landed roughly on the surface limply, out cold. The thug with the cigar froze; cold sweat started to seep from his facial nodes as he slowly backed away from his partners' bodies. His cigar slipped out from his quivering jaw. After several steps backward, he yelped as he bumped into a figure behind him and immediately turned sharply.

The boy looked up at him with a chilling smug smile before driving a gut punch that knocked the absolute wind out of him. The thug doubled over, and his jaw gaped as far as it could, with his pupils shifted to shaking pinpricks from the pain. Slowly, he fell to his knees before his upper body hit the ground with a dud.

Killua looked down at the bodies with apathy, he only used soft jabs to take them down, and he didn't even use Nen. He knew this would be the outcome, but it would suck if anyone around here didn't use Nen. If that were the case, he'd come into constant time-wasting conflicts.

Sighing, he continued, leaving the thugs in a heap on the ground to whoever had to deal with them. After stepping out in public, Killua took several glances to each side of the road, figuring out which way to turn. He ultimately decided to take a left.

He strolled on with an aloof posture, his eyes half-lidded with his hands returned to his pockets. Seemingly unaware of his surroundings. On the contrary, Killua had his senses stretch out to all directions along the way. He felt several eyes on him as he passed by several people while others simply ignored him.

After a long while of glancing and aimlessly wandering, he looked around and couldn't decipher the language. He wouldn't be surprised if he had already passed by several libraries; a vein popped through his forehead. That settled it; he might have to break into a place and use someone's computer.

Killua looked around once more and immediately spotted an entrance to what looked like a restaurant.

Perfect.

He approached the entrance and frowned when he realized it was quite crowded. This will have to make do. He had to locate the manager's office without detection, take them out, and use their internet services.

Killua checked his pockets and realized he still had a few jenny to spare. He paused after he held out a small handful of jenny. "Now that I think of it, would jenny be accepted currency around here?"

Whatever.

He could just easily snatch up a few goods along the way. Or he could pickpocket others for money for an easier way to keep himself sustained.

Killua blinked as he heard sirens from a distance. He turned and spotted a couple of dark cars with lights closing in from down the road. They were flashing red and blue.

Cops. They appeared to be driving in the direction he came from. Of course, he'd figured someone would notice the thugs unconscious in the alley and notify the police.

Oh well, he doubted they'd figure him out anyways. He was no blacklist hunter, but he'd put down anyone that would annoy him. Speaking of hunters, he still possessed his hunter license in his shorts; would it work around here? "Scratch that. They wouldn't understand that," he noted.

He entered the restaurant, his lips curled up slightly, and he stood corrected. The place was packed with people; tables were set in rows all over the place. Some tables weren't occupied, while others were filled in with individuals, couples, families, or groups of friends. His eyes narrowed at the long line leading toward the host.

Making sure no eyes were on him, Killua zoomed past the crowd at a speed that would cause his body to become an invisible blur to the untrained eye. He reappeared by a corridor on the far side of the room. He snickered as he held up a sandwich in his hand that he had taken from an unsuspecting family occupying a table in his path. "Losers," he muttered with a quiet snicker.

After quietly guzzling the sandwich to himself away from the public, he neared a water fountain clung to the wall by the restroom doors.

Satisfied with the refreshments, Killua continued down the narrow corridor. In contrast to the lively dining room, drowned in the abundance of the rather annoying noise of customers. This hall was relatively quiet and not occupied by people. Not that he minded; he much preferred this type of environment to the former.

"Now, where is the office?"

He guessed it had to be at the far end of the corridor. He stopped by the last door. Killua took a deep breath and gently knocked on the wooden barrier. Once he saw the knob make a twist, he tensed in preparation. The door opened to reveal a man in somewhat disheveled business attire with a buzzcut. He stared dumbfounded toward the space in front of him; he leaned out through the door frame, shifting his head towards the corridor.

He groaned before re-entering the room, "Stupid kids…." He grumbled before closing the door, revealing Killua, who hid behind it. Before he could process the fact that he had been invaded, Killua swung his hand to land a light chop to the side of his neck. Killua caught the man before he fell and gently sat him against the wall.

Killua nodded to himself at his accomplishment with a satisfied grin, "Sorry, buddy, but I have to borrow your stuff for a minute."

Killua took in the room. The office looked quite homey than he thought it would be. A coffee table sat in the center of the room with two leathered sofas surrounding it. By the door, a television stood on top of a TV stand; it was currently switched on and was on a channel that seemed to be a news program. The walls were decorated with many picture frames, art pieces, and various collectibles. There was a simple office desk by the far wall of the room with a fridge that leaned against the wall beside it. And there, sat on the desk, was his target; there was conveniently a back door which was on the left-hand corner behind the desk.

Killua approached the desk and fell upon the swivel chair, immediately focusing his blue eyes on the desktop screen. Even the visual interface of the computer wasn't familiar to him. He looked down at the keyboard, and his heart sank. He growled. How could he not take into account that the letters on the keys were all in this same stupid language? Why didn't he consider that before taking action?

He took a breath to calm his nerves. He'll just improvise and force himself to learn the basics right here before he can learn the advanced portion at a library. He surveyed the desk, as cozy as the office felt, the desk was smothered in a scattered heap of papers. It wasn't hard to find an unused notebook. He shifted through the mess of stacks.

After finding a pen, he began scribbling down words in his language on the page. Killua completely devoted his time to his study. So much so that he didn't even bother himself to track the time. He tried hard to compare the two languages while also attempting to pronounce the words he would see on the screen. He wished himself he was a computer genius as much as Milluki was.

After comparing many words and a good deal of time that passed, Killua started tracing down English words in the notebook he would see on the computer. He heard groaning from the other side of the room. Sighing, Killua got up once again to chop the man down a second time.

After another considerable amount of hours of studying, Killua looked up at the clock. He was relieved to know that the clock's digits remained the same. The sun must be down by this hour, and he stared at the man that lay on the couch. He had chopped him down on numerous instances throughout the entire period. Killua had to be honest with himself; he grew to sympathize with the man. He would undoubtedly wake up with an aching neck in the morning.

Killua stood up from the seat with the notebook and pen in hand and went to take his exit out the door.

"Breaking News!" The report exclaimed through the television, which had caught Killua's attention before he would egress from the office. By the looks of how this was presented, this seemed rather important. The man stood in a courtyard of a rather dim castle-like mansion in the background. "This coming in, we are live, here at Arkham Island! Earlier this evening, Patient 425 at Arkham Asylum had escaped. I repeat, The Joker has escaped from Arkham Asylum once again. It was...reported that a man dressed as the patient was found tied up inside the suspect's cell room with a bomb taped to his chest. Thankfully, the Batman arrived shortly after and was able to defuse the bomb in the nick of time."

While Killua failed to understand a word being said, just by the simple bases of this coverage, he perceived that a criminal had escaped from prison. The program showed off an unoccupied cell that was supposed to house some convicts from causing harm to the citizens.

The program began to show photographs of the victim's identity, he was a bit on the obese side, and his haircut was of the power donut with a single lock of hair that remained on his balding top. He wore a crestfallen expression in the photo. "The victim's name was Charles Collins. He had been rushed off to the emergency shortly after being recovered. We wish him well for a speedy recovery."

Next was a mugshot of a man being displayed; he had a narrow-shaped head with a pointed chin, green-slicked, messy hair, and his skin was paler than his relatives. Killua blinked, slightly put off by his appearance, he was sure he had never met this man before, but his outward appearance sure reminded him of a certain someone very familiar to him. The only difference was the way he held his grin; in contrast to the sly, slithery grin that Hisoka usually wore, this man seemed more deranged. His lips were stretched wide across his cheeks, shamelessly showing off his stomach-churning teeth, and his soul-piercing eyes told him that they were derailed from reality. Madness.

"For those of you that are watching, be sure to lock all your front and back doors, windows, or any other entry that would lead into your home, for he is armed and dangerous. If you see anyone or anything that bears any resemblance to The Joker, you must inform the police immediately...stay safe." The reporter's grim expression was the last thing seen on the screen before the program was cut to showcase the local advertisements.

Killua made a sound of indignation through his lips before he finally took his exit out the backdoor. The full moon hung high in the night sky, and the noticeably cooler air attacked his exposed face. He turned his head from one side to another before springing up to the roof and stared towards the illuminating lights on the numerous buildings.

He was going to have to seek another place to stay nearby. He was done with that office. He had written all he could in the notebook that would hopefully provide for his learning.

Something caught his attention in the corner of his eye. Killua blinked and gazed up bewilderedly to his left. At a far distant part of the city was a giant bright-blue ray of light that extended to a silhouette of a bat towards the clouds.

"A bat insignia in the sky? What the hell is that supposed to mean?" Killua contemplated if he should journey to the location but shrugged and bounded to an opposing direction. He decided that it wouldn't be anything to his concern. He was too peeved to let himself waste any time. He continued searching for a place for him to inhabit temporarily, and before long, he spotted an apartment complex that looked cozy enough.

Smiling to himself, Killua approached the area at a rapid pace, easily bypassing the security to an unoccupied suite.

Elsewhere in Gotham City, Batman landed gracefully on the rooftop of the GCPD and immediately approached a middle-aged man that awaited him by a klieg set on the roof. "You took longer than you would usually show up." Commissioner Gordon said after he noticed his presence.

Batman stopped beside him. "I was busy."

"So I've heard. We found no traces of Joker, by the way…" Gordon started with a grave expression.

"I expected that. It won't be easy, but I'll find him. He usually wouldn't let himself be known until he had already put his next scheme into action."

Gordon nodded solemnly, "That's what I'm worried about…."

"Was that the only reason you called me, Jim?"

"No, actually. Earlier on, the boys came across an interesting case, and I believe you will find this intriguing. We suspect it's another vigilante that made a debut for himself earlier today. However, we couldn't be sure if that was the case." Batman narrowed his eyes suspiciously as soon as the word 'vigilante' rolled out Gordon's tongue.

Batman stretched out his gloved hand from his cloak-like cape, "Documents?"

Jim held out a folder containing the current story to the dark-cloaked hero. "Right here, from what we gathered at the scene, our detectives presumed that the fight that happened in the alley was quick and brief. None of the surroundings were affected by the fight, no trash cans were thrown, no broken windows, and it didn't stir a ruckus loud enough to disturb the nearby public. The only things that could contain any evidence were a knife and a cigar we found on the ground. " Batman took it and opened the file to inspect it.

There were three photos of men that were known convicted criminals, all with their names and information listed under their profiles; they were identified as the victims in the case. It also marked the location of the crime scene, "All three men sustained major trauma on single parts of their body. One of them had his cervical cord almost fractured, one is suffering a bad concussion, and one has a large bruise on the abdominal area. They'll be fine. They all will be brought into custody by next week."

Batman hummed as he skimmed through the information. "It's like they were taken down by a single blow," he thought aloud.

"My thoughts exactly. Any idea who it was?"

Batman shook his head and lowered the manilla folder to eye the commissioner, "No. I know several people that are capable, but I reminded them that they shouldn't cross my city's borders to do my job. I'll head there myself to survey the area, scour for some clues that your men might've missed."

Gordon nodded. He looked down as he stuffed his hand in his trench coat, took out a lighter, and lit the end of his cigar. "By the way…" Gordon paused as he looked up, staring at the now-vacant space beside him. He took a puff and let out a tired sigh. This happened every time they would have a meeting. He had grown accustomed at this point, so he wasn't at the slightest bit astonished.

What are your thoughts? Don't forget to review to let me know, constructive criticism is welcomed.

Before I end things here, I would like to pay respects to the passing of the legendary Batman voice actor. Rest in peace, Kevin Conroy.