Hard T for heavy themes, psychological horror, and some graphic imagery.
More specific content warnings are available upon request, but will be omitted here to avoid giving out spoilers.

(Psst! Read in dark mode! ...or don't. You do what you want. :3)

EDIT 10/14/17: I've been asked a few times whether I'll be continuing this fic, so I'll confirm right here that yes, I am continuing this fic. I know I'm slow and it's been about a month since I posted this chapter, but for future reference this story isn't over until I've marked it "Complete". Trust me, this is a very small portion of the story as a whole. ;)

A/N: So I was attacked by this evil plot bunny around late July or early August 2016. The thing is, I'm not usually a writer, drawing is more my thing, so it took forever to write this. But I had to write it because I'm trash and a horrible person (and I'm sure you can't read this whole story without agreeing with that last bit :'D ;-; ) and I'm sorry.

Based in the '03 series, specifically the Japanese version. If you're wondering why I'm being so specific, go check out a comparison between the original Japanese version and the English localization. They're different enough that it affects characterization and even plot. That said, the very first line of the story is actually lifted straight from the '03 series subs, I kid you not.

That aside, this chapter nods to a few things for your enjoyment. (...okay, and mine too while I was writing. xD) Let me know if you noticed some… or don't, I'm not going to make you. :P

Oh, and you'll probably notice that I've included a few Japanese words in the story. I've mostly done this with titles or suffixes because it helps give the English dialogue of this story a bit of a "dialect," if you will, that matches up with the show. Anyway, I'm not going to screw anyone over who doesn't happen to know these words, so I put a little "glossary" at the bottom of the chapter that explains each Japanese word that I chose to use in the story.

Yeah, yeah, and here's the blanket disclaimer: I'm a lazy 19-year-old who lives in a cave under my bed, do you really think I own Astro Boy/Tetsuwan Atom? (remember it! :P)

Enough of my rambling, here's the story already:

Corrosion

Prologue

"I shouldn't have been born."

No matter how much time had passed, no matter how many times he had tried to bury the notion, it always resurfaced.

He had voiced the thought once; the first time he dared explicitly think it. He knew better now. He didn't want to worry anyone. Atom had seen how appalled Professor Ochanomizu had been that he would—could—think such a thing.

The Professor's reassurance had dulled the stinging surety of his conclusion, but the doubt was still there. He had put on a smile and tried to leave it behind him, but the thought had already latched on like a parasite. He could cover it up, but it still corroded him from the inside out. Rotted, even, because the corrosion felt a lot less sterile than rust.

It was getting harder to hide the gaping hole.

Chapter 1

The school bell brought Atom out of his thoughts. The loud chattering and various social sounds now met his ears as his classmates began to pack up or attempted a bit of mischief. Miss Midori waved to some passing students as they began to leave. Still in a bit of a daze, Atom stood and set his backpack on his desk to put away his notebook. As he pulled the backpack over his shoulder, Atom heard familiar voices call him from behind.

"Hey, Atom!" Ken'ichi and Tamao called.

"Trying to leave without us?" Shibugaki questioned in jest.

Atom turned to see the trio waiting behind him. His expression lit up and he warmly replied, "Hi guys! Ready to go?"

"Ready when you are," Ken'ichi answered with a smile.

Pulling the second strap over his other shoulder, Atom joined his friends and headed for the door, waving to Midori as they passed her by.

"So, how did you guys do on the homework?" Ken'ichi asked.

"The math assignment?" Atom asked for clarification.

Tamao snorted. "Yeah, I think I know someone who might need a little help with that," he replied with a smirk, nudging Shibugaki with his elbow. "How'd you do on that math assignment, Shib?" he queried in an impish tone.

Shibugaki's face flushed, hesitating as all eyes turned to him. Then his mouth twisted into a mischievous grin. Opening his bookbag and reaching inside, he responded, "I gave all the answers the assignment needed." He then pulled out a sheet of paper and proudly presented it to the other three boys. They all paused to observe the piece; a graphite depiction of Hyotantsugi doodled directly over almost the entirety of the neatly printed math problems.

Tamao immediately burst into a fit of laughter, Atom's and Ken'ichi's eyes widened, and they both had to stifle their own laughter.

Almost incredulously, Ken'ichi asked, "You seriously did that?"

Between the question and Tamao's cackling, Atom accidentally let a titter escape. This set the other two off, and Ken'ichi had to fight to subdue his laughter long enough to speak.

"Shib, maybe you should take some of your assignments seriously."

Atom stepped through the doorway and was greeted by Uran, who was sitting on the couch with the beginnings of a flower necklace in her hands. Various other blossoms and discarded stems lay strewn about her.

"Hi onii-chan!" She grinned and held up the small string of flowers. "Look what I'm making!"

Atom couldn't bring himself to say anything about the mess yet. He smiled and walked over to sit down beside her, careful not to crush any of her flowers that were laying on the couch. "Having fun?" he asked.

Uran nodded enthusiastically and said, "I'm making it for Ochanomizu Hakase!"

Atom, unsure of how to respond to this information, replied simply, "Oh." He then asked, out of slight suspicion, "Where did you get the flowers from?"

Uran took on a sheepish expression.

Just then, Robita entered the room, having heard the last snippet of the conversation. Sounding almost tired, she said, "Uran-chan picked those at the park before I could stop her." Shifting her gaze to Uran and addressing the little girl android, she continued, "Now, don't forget to pick up after you're done. I've still got more to do, and I'd better not find out that you left a mess here just because I wasn't watching."

Uran nodded with a guilty little smile.

Robita gave a long-suffering sigh as she began moving away, then paused and turned back to say, "Oh, welcome home, by the way, Atomu-kun."

Atom smiled at her, then looked back at Uran again. Her expression was one of total concentration as she had resumed stringing her flowers together. Atom shook his head good-naturedly and voluntarily began sorting Uran's contraband, pulling the stems out of the group and setting them aside.

"Thanks, onii-chan," Uran said.

Atom nodded politely in return before standing back up and leaving to take his backpack upstairs to his room.

Walking through the doorway, Atom set his backpack down on the floor to open it up and double check for homework. Opening a folder, he found only a single sheet on the side designated for assignments not yet turned in. It was fully and neatly filled out.

He blinked. Right, the math assignment. He remembered now, he'd easily completed the assignment in a fraction of the time given in class. It was a completely technical subject matter and therefore didn't require much thought on his part. Today was an easy day, there wasn't really any reason he should have forgotten that it was the only paper assignment given. His friends had even been joking about the same assignment after school.

Atom furrowed his brows in slight confusion, then put the folder back into his backpack and closed it up. Briefly closing his eyes and rubbing his hand across his face, Atom crossed the room and climbed up into the window sill. Maybe he just needed some time to clear his mind.

When Atom came back down the stairs, late afternoon light filtered through the windows. He saw that Uran no longer sat at her spot on the couch. Surprisingly, she'd only left a few stems behind. He had to smile to himself in amusement that that was actually an improvement.

"When is Hakase coming home?" Atom heard Uran's voice from the kitchen.

"He has a shorter work day scheduled for today, so he'll probably be home soon," Robita replied.

Atom glanced at the kitchen to see Uran brighten at that. Robita busied herself retrieving items from cupboards and beginning to prepare dinner. Uran watched with what was probably too much interest. When she set her newly-completed flower necklace on the table and began walking towards Robita, Atom picked the stems up off the couch.

"Oooh, hey Robita, can I help?" Uran asked.

"Oh! Well, that is..." Robita trailed off. Despite her comparatively limited expressiveness, she was clearly uncomfortable with the current situation.

At that moment Atom walked into the kitchen and said, "Uran, you forgot something." He held out the stems for her to see.

Uran turned around and exclaimed, "Oh!" before reaching out to pick up the stems and continuing more quietly, "Oops."

Robita visibly relaxed and seemed to send a silent thank you to Atom.

At that moment, Professor Ochanomizu came in through the front door. Stems forgotten, Uran spun around, quickly grabbed her flower necklace, and sprinted over to him. "Hakase! Look, look! It's for you!" she exclaimed. Before Ochanomizu had much of any time to react, Uran had sprung into the air and attempted to place the necklace over his head, but fell short and left the floral gift perched on the nose of a very confused professor. Uran giggled when his eyes went a little crossed in an attempt to see what exactly was sitting on his nose.

After this spectacle, Atom decided that the best course of action was probably just to drop the few remaining stems in the trash before greeting Ochanomizu. Robita followed.

"Ah, what's this?" Ochanomizu asked Uran, picking the gift up off of his nose.

"A flower necklace," she replied happily. "I made it for you!"

"Really? Well, that's very kind of you," he chuckled.

"Hi, Hakase," Atom said as he walked up.

"Oh, hello, Atom," Ochanomizu replied.

"Welcome home," Robita joined in before asking for his coat and hat.

"Thank you, Robita," he said, handing her his hat before turning to Uran with the necklace and asking, "Would you hold this for me?" She took the necklace and he removed his jacket to give it to Robita, who went to put away the clothing items.

"Hakase, can I put this on you?" Uran asked, holding up the flowers again.

He smiled and said "Alright, let me sit down first." He walked over to sit at the couch, followed by both Uran and Atom.

Uran wore a grin as she, more carefully this time, pulled the ring of flowers over the professor's head. She clasped her hands together as she admired her handiwork.

"Well, isn't that nice?" Ochanomizu said. "Did you have fun making it?" he asked.

Uran nodded.

"That's good," he replied. "And how about you, Atom?" he asked, turning his attention to the robot boy. "How was your day?"

Atom looked up at him. "Oh. Well, today was pretty easy at school. We only got one homework assignment, and it was math. I finished it in class," he replied.

"Oh, that sounds nice," Ochanomizu said warmly.

Atom smiled. The he saw Robita heading back to the kitchen.

Ochanomizu followed his gaze. "Robita, would you like some help?" he asked.

Robita turned and replied, "Oh, okay. If you'd like to."

Before Ochanomizu could even get up, Uran asked, "Can I help?"

Atom looked from Uran to Ochanomizu.

Ochanomizu paused, then said, "Alright, but only if you're very careful and listen to everything Robita tells you."

Uran nodded again and her grin widened.

Ochanomizu stood up and headed for the kitchen, followed by Uran and then Atom. "So what are we making, Robita?" he asked.

"Croquette sandwiches," Robita replied.

Ochanomizu smiled and briefly closed his eyes at that. "Ah, that takes me back. When I was still attending University, the cafeteria there served some exquisite croquette sandwiches."

The dishes were put away and the setting sunlight had waned a little further into evening. Professor Ochanomizu, still wearing Uran's hand-crafted gift, had flipped on a small ceiling lamp in the living room and donned a pair of glasses to assist his eyes with reading an old novel. Uran hummed a tune softly while doodling in her sketchbook, with Robita pausing next to her to observe. Atom rested his chin and crossed forearms on the back of a seat near the window, observing the sky and distant surroundings.

A beeping sound coming from the center table caught everyone's attention, giving notification of an incoming video call. Ochanomizu picked up the noisy little device and peered at the caller ID that now displayed on a small screen. He then located the input button for the integrated communications system before pointing it at the ceiling-mounted television set and pressing the button. The set immediately lowered to a convenient viewing level and the screen cover opened as the screen powered on, revealing a familiar face.

"Hello, Reno," Ochanomizu greeted cheerfully.

"Reno!" Uran blurted loudly, then began waving cheerfully.

Atom smiled, moving closer before saying, "Hi, Reno."

"Hey everyone," Reno replied, pausing as Uran continued waving. "You too, Uran," he chuckled.

Uran slowed a bit before receiving a light tap on the shoulder from Robita. Then, as if coming to some realization, she retracted her hand, looking slightly abashed.

The corner of Atom's mouth quirked up in a crooked, amused half-smile.

"How have things been for you, Reno?" Ochanomizu asked. By the sound of his voice, he shared the amusement and was trying very hard not to embarrass Uran any further.

"Great!" Reno beamed, "We've been testing some new underwater sensors in the conditions at several places along the eastern shoreline, and it looks like everything is working how it should."

"Wonderful," Ochanomizu responded. "Do you have any further plans over there?"

"Oh, that was actually part of what I was calling about," Reno replied, scratching his head. "I mainly came out here to test and adjust the sensors to work reliably in the ocean. Now that they're working, I felt like it's time to pack up and go back to Metro City."

Everyone seemed to light up at that, and Ochanomizu answered, "Of course! We look forward to having you back around here."

"Alright! I'll probably be back in about 2 days," Reno said, giving everyone a thumbs-up.

"Oh, that reminds me, Reno," Ochanomizu said. "Some-" he paused briefly, before resuming, "Some older-model robots are being brought to the Ministry for inspection. They're supposed to arrive tomorrow. I thought you might benefit from taking a look yourself when you get back. There's a chance we'll be developing a patch for them."

Reno nodded, saying, "Okay, I'll make sure to do that." He then continued, "So, how have things been, otherwise?"

"Oooh!" Uran stood back up and ran over to Ochanomizu, then tugged lightly at the flower necklace that had, by that time, become slightly wilted. "I made this for Hakase!"

"Did you, now?" Reno asked good-naturedly. "I was wondering where it came from."

"And I got to help in the kitchen!" Uran continued excitedly.

Robita chuckled a bit when Reno's smiling expression became the slightest bit concerned. "Yes, and she managed to keep her workspace pretty clean, too." Turning to Uran, she continued, "It seems you're putting the pound-cake incident behind you after all."

Uran snickered and blushed a bit, and the others responded with their own laughter.

"How about you, Atom?" Reno asked.

"Oh, pretty good. I haven't needed to take any time off from school lately, and things have been going well," Atom said.

"I'm glad to hear that," Reno replied. "Well, I'd better start getting things ready to go. The sensors themselves may be fairly small, but the testing equipment took a while to set up, so I'm guessing it'll take a while to pack as well. It was nice catching up with you all."

"Alright. We'll see you later then, Reno," Ochanomizu said.

"Okay, see ya!" Reno said, waving.

"Bye!" everyone else responded.

The door shut quietly behind Atom as he retired to his room for the night. Sighing, he began to remove his school outfit. The day had gone by in a bit of a blur. He stepped forward and climbed into bed.

It had been a few weeks since the incident with Ashura and Ganymede, and losing his memory. Though his recent memory had been recovered instantly when Professor Ochanomizu had repaired him, Atom's older memories had remained a bit more elusive. The memories seemed to be resurfacing gradually on their own, though. A couple of little pieces seemed to come back each day. However, some pieces were not as welcome as others.

How long has it been? About a week?

Although he'd still felt the ambient discomfort the memory emitted while it had been buried, its recovery had been jarring, to say the least. Wandering into the deserted home, whether after his twin apparition or a figment of his imagination, had been an event in and of itself. And then...

Atom turned over to face the sky light in the ceiling.

But that's in the past. Today was good. I have my own life now.

His brows furrowed.

But is it really my place to decide?

Pushing the thought aside, he focused his gaze briefly on the sky above before closing his eyes.

Atom's eyes opened to darkness. He blinked. Gradually, his vision adjusted to the gloom. The dim light cast from the window was now visible, touching the wall with a soft, ethereal glow. It was dead quiet, only the steady pulse of his heart broke through the silence. Feeling restless, Atom slowly sat up, dropped his feet to the floor, and sauntered toward the window. The padding of his boots on the carpet seemed to echo off the walls. Drawing near the window, Atom observed the cold, white moon. Shifting his gaze to other parts of the sky, he couldn't help but feel that something was off. Atom pondered this for a moment, but he couldn't quite put his finger on it as he carefully studied the softly gleaming stars and the frosty light they cast on his skin. It was as if a sort of fog had settled over his mind. Releasing a softly echoing sigh, Atom moved to pull himself onto the windowsill as he often did on sleepless nights.

A terrified shriek tore through the silence.

Atom's attention immediately snapped to the source of the awful cry. He abandoned the window and bolted for his door, heading frantically toward Uran's room.

Bounding through the doorway, Atom's eyes were greeted by a dark figure looming over Uran from the side of her bed. Panic, shock, and anger flooded Atom's racing heart.

"Get away from my sister!" he snarled, his voice burning with a protective rage. The figure barely seemed to acknowledge his presence. It calmly turned its head toward him with an insidious grin and raised a finger to its lips.

"Shhh..."

Atom's glare hardened further and he sprang to seize the shadowy figure, only for it to seemingly disappear right in front of him. Atom, bewildered, turned his head sharply around to find the intruder behind him. He lunged again, but to no avail as his hands rent only thin air. Eyes wild, Atom spun around and formed his arm cannon as he located the shade across the room and away from Uran. As he took aim, it merely tilted its head with that maddening grin still plastered on its face. Once again, it seemed to disappear. Atom whirled his head around to look for it. He didn't find it. The figure seemed to be gone.

Atom's cannon reverted to his usual arm and hand. He had been focused on the shade, but now that it wasn't here Atom couldn't help but notice that the incident had gotten no reaction from Uran. His breath hitched. He slowly turned around and looked down at Uran.

Her face was still frozen in utter terror. Her jaw was dropped in a now-silent scream. Her eyes were wide and glassy. Atom noted in horror that her pupils and irises were no longer distinct; they had faded together.

She had dead eyes.

"Hakase!"

Frantically, Atom pulled the covers off of Uran, scooped her up, and ran to take her to Ochanomizu. Her head and limbs hung from Atom's grasp like those of a ragdoll.

"Hakase!" Atom cried out again, tears beginning to stream down his face. He shoved the door open to the professor's room. And there it was. The obscure figure had restrained the wide-eyed professor, with a hand forming a tight seal over his mouth. Atom began trembling and his face contorted in pain and rage.

"Who are you?!" Atom shouted.

The figure faced him but ignored his question. He tried to identify it on his own, but he came to realize that it was like trying to catch a mirage. It had what seemed to be recognizable as a face, but every time he tried to focus on the identifying features, they seemed to dissipate.

"What do you want?!" Atom, again, shouted.

"That is the right question," replied the figure. Similarly, the voice was a sort of mirage. "I have a question for you." it continued.

"What?" Atom growled. He tried to adjust his grip on Uran to support her head, but found that he was trembling so violently that it was becoming difficult to maintain a solid grasp on her limp form.

"What do you protect, your secret or your family?"

Atom was unsure of what 'secret' the mirage referred to, but he was certain that no secret was worth putting his family and friends at risk. He stole a glance at Uran before tearing his gaze away, realizing it had been a bad idea. He tried to keep his voice from quavering as he answered the mirage grudgingly, "Family."

Silence.

The shade dropped its grin, as if finally taking the situation seriously. An incredibly bitter tone followed, almost a whisper.

"So naïve."

The figure removed its hand from the professor's mouth, who was at a loss for words. He merely gazed sadly at Atom and Uran.

Atom then realized what was happening. The arm drawn away began to morph. The process was all too familiar. Atom froze. His eyes widened and his skin blanched. He stared in horror as the dark figure formed a lethal weapon out of its arm.

His arm cannon.

The professor, once again, struggled desperately to escape, but it was in vain.

"No! Stop!" Atom shouted.

The shade pointed the weapon.

"You did this." it growled at Atom.

"NO!"

A blinding flash.

Atom flew up into a sitting position in his bed, coughing out a choked wail. Eyes wide and hyperventilating, he pulled his knees up to his chest and held them tightly. He squeezed his eyes shut and more tears flowed as he stifled another wail. Soft night sounds greeted his ears, as if attempting to comfort him with contrast to the earlier deathly silence. Atom would not be comforted. He took a shaky breath. They just wouldn't stop. They only got worse. And they were all too plausible.

Glossary:

Hakase: Professor; in this case, referring to a scientist.

Onii-chan: Brother, or "big brother".

-chan: Endearing, usually (but not always) female honorific. Generally used to refer to children, family members, or friends. In childish language, it's often attached to terms of kinship. (ex.: onii-chan)

-kun: Endearing, usually (but not always) male honorific. Male equivalent of "-chan", though "-kun" is not attached to terms of kinship like the "-chan" honorific sometimes is. Within schools and companies, men might also address women of a lower rank with the "-kun" honorific, but women generally don't use "-kun" to address each other.

Note: I use the name "Atom" in both narration and dialogue; however, in some cases I'll write "Atomu-kun," rather than "Atom-kun". I chose to do this because the sound just seems to flow better when "kun" comes after a vowel than a consonant. I'll be consistent in doing this so you don't have to see me keep switching between the two whenever I write "Atom" with the "kun" suffix.

P.S. If I have any of these descriptions wrong, please let me know. To the best of my knowledge, they are correct, but I'm not exactly an expert in Japanese, either.