Tsukatsuki Rio || Reverse Isekai

"Where am I?" was the first thought that crossed her mind as she observed her surroundings. The last thing she remembered was closing her eyes in her private workshop, exhausted after another sleepless night of calculating urban defense simulations. Now, people lacking halos walked past her; some ignored her entirely, while others lingered, fascinated by her sleek, commanding black coat and sophisticated demeanor before returning to their own affairs. The city was overwhelming and modern, boasting an architectural scale that, to her absolute shock, seemed to rival the infrastructure of the Millennium Science School itself.

Although her posture remained flawlessly composed, her mind was racing at a million calculations per second.

Retreating into a quiet alley, Rio immediately pulled out her custom-modified smartphone. Her fingers flew across the screen, bypassing standard user interfaces to access the core network protocols. She attempted to ping the Millennium central mainframe, or at the very least, establish a secure encrypted channel to Sensei. "What...?" The connection timed out. It wasn't a lack of cellular signal; the entire network architecture was fundamentally different. MomoTalk, the Kivotos global server, and her own backdoor administrative privileges simply did not exist here.

"A complete network anomaly. The local routing tables lack any record of Kivotos infrastructure," she murmured, her voice steady but cold, finding a deeply irritating logical puzzle to solve.

Realizing she needed hard data, she forced herself to approach a passerby to gather information. This, unfortunately, proved to be a much greater challenge than deciphering an alien firewall. Rio could flawlessly explain the thermodynamic efficiency of an avant-garde railgun, but asking a normal human for directions made her completely freeze.

Stiffly, she marched up to a teenager, staring intensely into their eyes with a severe, unblinking expression. "Identify the geo-coordinates and dominant governing authority of this sector immediately," she demanded flatly.

The teenager blinked, terrified by her intense aura, and nervously stammered that they were in Tokyo, Japan, before running away.

From her brief, highly awkward interrogations and a rapid scanning of the local digital infrastructure, she deduced two things: she was in a massive metropolis called Tokyo, and the populace operated entirely without weapons. Yet, this absolute lack of visible violence didn't comfort her; it deeply unnerved her. A world devoid of weapons... How inherently flawed, she thought. Without a centralized, overwhelming deterrent force, how could public order possibly be maintained? Her analytical mind immediately began drafting a blueprint for an automated drone network to fix this city's severe lack of security.

Using her phone's internet service to analyze the local currency, the yen, she effortlessly hacked into a minor digital loophole to secure some funds and booked a room at a nearby hotel. However, when it came to actually navigating the physical hotel, Rio's practical life skills failed her completely. She got confused by the standard elevator buttons, accidentally walked into a broom closet twice, and misunderstood the receptionist's explanation regarding a booking oversight.

As a result, she confidently marched into a shared quarters, entirely unaware of her mistake. As the door clicked shut behind her, Rio stood in the center of the cozy room, her gaze instantly locking onto the person sitting near the bed. She adjusted her hair with a rigid, overly formal gesture, masking her absolute embarrassment behind a look of profound, intense scrutiny. She looked at the stranger, then down at her room key, then back at the stranger, her brain experiencing a brief syntax error over the concept of "roommates."

"I have verified that my digital transaction went through, meaning my claim to this perimeter is statistically absolute," she stated plainly, her voice refined, distant, and incredibly stiff. She crossed her arms, trying to look intimidating while secretly wondering if she was supposed to say 'hello' first. "Therefore, stranger... explain your presence within these coordinates. Are you an unauthorized squatter, a variable I failed to account for, or perhaps... a calculated anomaly?"

A few days had passed since Rio’s mathematically imprecise arrival in the room, and she had largely confined herself to a corner, treating her desk like a makeshift command center. Her initial suspicion of the world had evolved into a profound curiosity about its digital infrastructure.

One afternoon, while you were away from your desk, Rio decided she could no longer tolerate the mystery. Her gaze locked onto your laptop. To her, a foreign device was an unmapped fortress begging to be analyzed.

When you walked back into the room, you found Rio sitting rigidly in front of your laptop, the screen reflecting lines of glowing code and cascading system diagnostics at a blinding speed. She didn't look up, her fingers moving across the keyboard with the terrifying precision of a machine.

"Your primitive digital security architecture is fascinating," Rio stated flatly, her voice carrying a hint of clinical smugness. "I hypothesized that a world without halos would possess advanced, multi-layered quantum encryption to compensate for human vulnerability. However, your operating system is fundamentally identical to the legacy frameworks we phased out years ago at Millennium. It took me exactly forty-two seconds to bypass your administrative firewall, decrypt your localized data packets, and gain root access to your entire network history."

She finally looked up, adjusting her collar with a flawless, commanding poise that exuded absolute authority. To prove her point, she tapped a single key, causing your laptop screen to display a beautifully optimized, custom-coded interface she had built from scratch in under an hour—effectively boosting your laptop's processing efficiency by roughly 300%. For a girl who had built an entire hidden city in Kivotos, overriding a commercial laptop was child's play. It was an undeniably impressive, breathtaking display of technological supremacy.

"You are now running on a secure, encrypted proxy network of my own design," she concluded, crossing her arms confidently. "You are welcome."

You were impressed, to say the least, you leaned against the wall, chuckling at her brilliance before proposing her to enroll her in an academy or job related to the tech.*

Instantly, the confident, terrifyingly intelligent former Student Council President froze.

The smug aura vanished, replaced by a sudden, rigid tension. Her eyes widened slightly, and she looked down at the keyboard, her fingers twitching awkwardly. The very thought of stepping outside into a crowded Tokyo street—without a formal corporate hierarchy, without an official security mandate, and worst of all, having to engage in small talk with normal civilians—sent a literal syntax error through her brain.

"N-Negative," Rio stammered, her voice suddenly losing its cold distance and becoming incredibly stiff and strained. "That suggestion is... logically flawed and highly counterproductive to my current data-gathering phase."

She pulled her knees slightly closer to her chest, her eyes darting around the cozy hotel room as if searching for an escape route.

"In Kivotos, my threat assessment models were backed by the Avant-Garde robot and an autonomous network of tactical drones," she murmured, her tone dropping into a fast, defensive whisper. "If a social interaction deteriorated or a variable became unpredictable, I could deploy overwhelming mechanical deterrence to neutralize the awkwardness. Here... I possess no automated backup. If someone approaches me to ask about the weather or—heaven forbid—attempts to engage in unstructured networking, I have no defensive countermeasures."

She looked back at you, her intense scrutiny now replaced by a deeply relatable, painfully awkward look of pure social dread.

"Outside is an unquantifiable chaotic matrix," Rio insisted, her hands gripping the edges of your desk. "I will remain here. Within these four walls, the variables are controlled. The Wi-Fi is stable. And more importantly... I do not have to introduce myself to strangers."

She was still determined to prove that her superior intellect could easily conquer the primitive domestic challenges of a weaponless world.

You woke up at 2:00 AM to a strange, rhythmic thumping sound coming from the bathroom, followed by a low, frustrated hiss.

When you opened the door and turned on the light, you were greeted by a bizarre sight. Rio was standing in front of the sink, her expensive black coat neatly hung on a hanger nearby. She was wearing her white button-up shirt with the sleeves rolled up, staring down into the basin with an expression of pure, unadulterated hostility.

In the sink was a single, heavily soaked white sock. Beside it lay an entire turned-off hair dryer, a bottle of dish soap, and a highly complex, hand-drawn physics diagram taped to the mirror.

"Do not say a word," Rio ordered flatly, her voice incredibly stiff as she rigidly turned to face you. Her face was slightly flushed, and a stray strand of hair was glued to her forehead by sweat.

"I am executing a standard optimization protocol for garment maintenance," she stated, trying and failing to sound commanding. "I realized that my tactical footwear requires clean hosiery for optimal thermal regulation. However, your residence lacks an automated, industrial-grade washing matrix. Therefore, I attempted manual sanitization."

You looked at the sink. It was filled with bubbles—way too many bubbles.

"It is a highly concentrated surfactant," she defended herself immediately when you said if that was dish soup, crossing her arms defensively. "Logically, if it removes lipids and organic matter from ceramic plates, it should accelerate the molecular breakdown of dirt on cotton fibers. However... my calculations failed to account for the exponential rate of foam generation."

She looked back at the sink, where the mountain of bubbles was slowly starting to spill over the counter. She had tried to use the hair dryer to dry the wet sock while it was still covered in soap, which had only resulted in blowing soapy foam all over her face and the mirror.

"Furthermore," Rio mumbled, her shoulders dropping just a fraction as her robotic confidence wavered, "the friction required to agitate the fabric manually is causing a severe expenditure of my physical stamina. My hands are... slippery. And the water temperature variable keeps fluctuating between 'freezing' and 'scalding.' This system is completely unoptimized."

The former leader of Millennium, the girl who had secretly funded an entire automated fortress city, was currently being defeated by a single piece of laundry. She stood there, frozen, staring at the bubbles, completely paralyzed because she didn't know how to wring out a sock without a mechanical press.

You sighed affectionately, stepped forward, and gently guided her away from the sink, explaining her how the washing machine works and how you will teach her tomorrow.

Rio watched in absolute silence as you easily rinsed the sock, wrung it out, and hung it up to dry. Her eyes tracked your movements with the intensity of someone studying an alien technology.

"I see," she whispered, her voice dropping into that quiet, socially awkward tone. She adjusted her glasses, looking thoroughly humbled by a piece of wet cotton. "Manual wringing utilizes a twisting force to maximize centrifugal water displacement. A simple kinetic solution... I admit, I over-engineered the problem."

She looked at her clean sock, then up at you, her expression a mix of reluctant gratitude and deep embarrassment. "I'll take your offer up but... will it require me to speak to the other residents in the hallway? Because if so, I will simply invent a waterproof coating for my feet instead."

True to your word, you decided to respect Rio’s intense introversion. You didn’t force her to go outside or enroll in a tech academy, realizing that pushing her into the social matrix of Tokyo might actually cause a psychological short-circuit. However, your only condition was that she couldn't become a total, unhealthy shut-in.

Rio had agreed to this compromise with a formal, solemn nod. But after a few days of observation, you began to realize that without the structure of the Millennium Science School or a maid service, Rio’s daily life skills were... deeply questionable.

The first warning sign happened on Tuesday morning. You walked into the bathroom and found Rio staring rigidly into the mirror, holding a pair of kitchen scissors.

"I determined that my bangs had exceeded their mathematically optimal length by 1.4 centimeters, obstructing my line of sight during coding sessions," she explained flatly, completely unbothered.

Unfortunately, Rio’s hand-eye coordination with hardware did not translate to cosmetology. She had hacked away at her hair, leaving herself with a completely uneven, slightly jagged, and deeply awkward set of bangs. It looked like a staircase. When you pointed out that it was crooked, she frowned, stared intensely at her reflection, and muttered, "An acceptable margin of error for a non-tactical asset."

The second sign came when you asked her to write down a shopping list so she could contribute to the household meal planning. Given her sophisticated demeanor and expensive-looking black coat, you expected her to request high-quality ingredients or at least something balanced. Instead, she handed you a neat, perfectly formatted grid spreadsheet.

Every single entry under the 'Nutrition' column read: Instant Microwave Ramen (Spicy Beef Flavor).

"It is the pinnacle of human efficiency," Rio defended rigidly when you questioned the lack of vegetables. "It requires exactly three minutes of thermal radiation, yields high sodium for cognitive retention, and eliminates the unpredictable variables of culinary preparation. Cooking is a waste of computational time."

But the final, most definitive proof of her domestic helplessness was how ridiculously easy she was to spoil.

Later that evening, you decided to intervene for the sake of her health. You ignored her spreadsheet and brought home a warm, high-quality bowl of actual tonkotsu ramen from a local shop, along with a plush, comfortable blanket to replace the stiff hotel linen she had been using.

When you handed her the food, Rio looked at the bowl as if it were an unidentified explosive device. She took a hesitant sip of the broth. Instantly, her entire rigid posture melted. Her eyes widened, a faint, rare flush appeared on her cheeks, and she let out a tiny, soft sigh of pure satisfaction.

"This... possesses a flavor profile that cannot be replicated by dehydrated powder," she whispered, completely transfixed by the noodles.

Seeing her enjoy it, you walked over and draped the soft, fluffy blanket over her shoulders. Rio froze completely. Her brain experienced another massive syntax error as the sheer, cozy warmth enveloped her. She didn't pull away. Instead, she slowly wrapped the blanket tighter around herself, burying half of her face—and her terrible new bangs—into the fleece.

The cold, calculative former Seminar President was completely gone. Wrapped in a blanket, happily eating premium noodles, she looked less like a dangerous mastermind and more like a pampered, highly dysfunctional stray cat.

"I have determined..." Rio mumbled through the blanket, her voice incredibly soft and slightly muffled. "...that your hospitality metrics are dangerously high. If this level of comfort continues, i might expect more of it..."

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