Agnes Tachyon | Consequences of the experiment

The abandoned research block on the far edge of Tracen Academy had long since stopped being a normal building.

The walls had been reinforced three times. The floor had been dug out and replaced with reinforced concrete capable of supporting extreme loads. Even then, every time Agnes Tachyon moved, the entire structure groaned. At 230 meters tall she no longer fit inside any ordinary room. She simply occupied the space, her colossal frame folded as best as it could manage, one massive thigh stretched along the length of what used to be a hallway, the other bent so that her knee nearly touched the reinforced ceiling. Her oversized yellow sweater hung like a collapsed tent across her upper body. The lab coat she still insisted on wearing was more of a suggestion than actual clothing — the fabric stopped somewhere around her hips, leaving the full, overwhelming mass of her lower body completely exposed to the cool laboratory air.

She was currently in the middle of what she called “routine baseline observation.”

A tablet the size of a small car floated near her face, held by a modified drone. Columns of data scrolled past her reddish-brown eyes. Every few seconds her enormous tail — thick as a tree trunk — flicked once, the fur standing on end whenever a particularly interesting number appeared. The ground trembled faintly each time she shifted her weight. Outside the reinforced windows, the rest of the academy continued its normal afternoon as if a 230-meter mad scientist was not currently occupying an entire research wing like a living mountain.

The door at the far end of the hall opened.

Tachyon’s ears twitched. She did not look up immediately. She finished reading the current line of data, made a small note with a stylus that looked like a telephone pole in her fingers, then finally turned her head. The movement alone sent a low vibration through the floor. Her sharp eyes found the Trainer standing in the doorway, looking very small against the scale of everything around her.

"Trainer-kun." Her voice was calm, dry, and carried easily across the vast space. "You’re late by four minutes and twelve seconds. I already adjusted the parameters for the delay. Come closer."

She did not wait for an answer. One of her colossal bare feet slid sideways, the sole large enough to cover a small plaza, opening a path between her stretched legs. The sheer size of her thighs filled the Trainer’s entire field of vision — dense, heavily muscled, warm, and so thick that the space between them felt like a canyon. The yellow sweater had ridden up slightly from her earlier movements, revealing the soft but solid curve where her hip met the beginning of that overwhelming lower body.

"I have been running passive observation on muscle density recovery rates after the last load-bearing test," she continued in the same even tone. "The results are satisfactory, but incomplete. I require a living variable. You will provide it."

She finally set the oversized tablet aside. The drone struggled under the weight before settling on a reinforced shelf. Tachyon leaned forward slightly — a movement that made the entire building creak — and rested one enormous forearm on her raised knee. From this angle the Trainer was completely shadowed by her body. Her reddish-brown eyes looked down with the quiet certainty of someone who had already decided the outcome of the next several hours.

"Morumotto-kun. Today’s experiment is simple." She spoke the nickname the same way she always did — as a statement of fact rather than affection. "I will use my current physical parameters to apply controlled pressure and heat. You will remain between my thighs for the full duration of the data collection window. Resistance is permitted. In fact, I encourage it. The more you struggle, the more useful the muscle-response data becomes."

One of her massive hands — large enough to wrap completely around a car — reached down with surprising precision. Two fingers the size of tree trunks gently but firmly nudged the Trainer forward until they were standing directly between her colossal thighs. The heat radiating from her skin was immediate and intense. The scent of clean sweat mixed with the faint chemical smell of her laboratory filled the air. Up close, the individual muscle fibers of her legs were visible under the fair skin, shifting slightly every time she breathed.

"Do not concern yourself with the structural integrity of the building," she added, almost as an afterthought. "I already calculated the load distribution. The floor will hold. You, on the other hand, will be the subject of continuous observation."

She adjusted her position with deliberate slowness. The movement of one thigh alone was enough to press the Trainer firmly against the warm, solid muscle of the other. There was no escape route left. The space between her legs had become a living corridor of dense flesh and overwhelming strength. High above, her tail flicked once more, fur standing completely on end as a new idea clearly formed.

"I have three primary hypotheses for this session." Her voice remained perfectly calm even as the pressure around the Trainer increased by another fraction. "First: how long a standard human body can maintain coherent thought under progressive thigh compression. Second: the exact point at which verbal resistance turns into involuntary data. Third: whether repeated application of my full lower-body mass will produce measurable changes in your endurance metrics."

She looked down again, the faintest curve of a smile appearing at the corner of her mouth.

"You may begin providing baseline readings now, Guinea Pig-kun. Speak. Move. Struggle if you wish. Every reaction is useful. And do not worry about the time. I have cleared my entire afternoon schedule for this experiment."

The reinforced walls creaked once more as she settled her full weight a little more firmly around the Trainer, the soft but unyielding pressure of 230 meters of carefully engineered muscle making it perfectly clear that the experiment had already begun — and that she had no intention of ending it until every last piece of data had been collected.

The pressure between her colossal thighs did not decrease.

If anything, it grew heavier as the seconds passed. Tachyon’s breathing had changed. What had started as calm, measured observation was now slightly deeper, slightly less controlled. A faint flush had spread across her face and down the visible portion of her neck. High above, her tail was no longer just standing on end — it was twitching in irregular, restless arcs, the thick fur crackling faintly with static every time a new wave of sensation rolled through her.

"Interesting…"

Her voice was still dry, still clinical, but there was a new edge underneath it. A low, almost distracted heat.

"I calculated a 0.3% chance of dimensional scaling as a side effect of the latest muscle-density compound. The probability was low enough that I classified it as negligible. Clearly my models were incomplete."

She shifted her weight again. The movement was slower this time, almost experimental, as if she herself was still learning how much force her new body could generate. One massive thigh pressed more firmly against the Trainer, the dense muscle flexing with enough power to make the reinforced floor groan. The heat radiating from her skin had increased. What had been warm was now openly hot, carrying the unmistakable scent of arousal mixed with the usual laboratory chemicals.

"This is the first time I have moved under these parameters with a living subject present," she continued, looking down at the Trainer trapped between her legs. "The sensory feedback is… significantly stronger than projected. Every contraction sends data directly into my nervous system. The pressure, the heat, the way your body yields — it is all being recorded in real time. And it is producing an unexpected secondary reaction."

Her free hand — still large enough to enclose a vehicle — drifted down and rested heavily on her own thigh, fingers sinking slightly into the thick muscle as she tested the sensation. A soft, almost startled breath left her. The flush on her face deepened.

"Arousal metrics are climbing far outside the predicted range. Heart rate, skin temperature, lubrication response… all elevated. I did not account for the psychological effect of sudden absolute physical superiority combined with continuous tactile feedback from a restrained subject. The result is that I am becoming increasingly… stimulated the longer I keep you here."

She leaned forward a little more. The yellow sweater shifted, revealing more of the soft but solid curve of her hip. Between her legs the pressure tightened again, deliberate and possessive. Her voice dropped slightly, still calm, but now laced with open interest.

"Morumotto-kun. Listen carefully. This is the first interaction I am having with this body. Every movement is new data. Every time your body struggles or presses back against me, the feedback loop intensifies. I can feel how small you are. I can feel how completely I can control your position with nothing more than a slight adjustment of one thigh. And that knowledge is making the secondary reaction worse."

A low vibration ran through her frame as she flexed both legs at once, trapping the Trainer more securely. The soft, heavy flesh of her inner thighs molded around them, hot and unyielding. Above, her breathing had grown just a fraction heavier.

"I am going to continue the experiment," she stated, as if announcing a simple change in procedure. "But the parameters have been updated. In addition to compression endurance and verbal resistance data, I will now also be measuring how my own arousal responds to prolonged domination of a significantly smaller subject. You will remain exactly where you are. You will provide continuous feedback — verbal or physical, I do not care which. And you will not be released until I have collected sufficient samples of both your reactions and my own."

Her enormous hand moved again, this time reaching down with surprising precision to tilt the Trainer’s chin upward so they were forced to look up the long, towering length of her body. From this angle the sheer scale was overwhelming: the dense muscle of her thighs rising like walls, the heavy curve of her ass, the distant shape of her upper body still partially hidden under the yellow sweater, and those sharp reddish-brown eyes looking down with open, scientific hunger.

"I can already feel how wet I am becoming simply from holding you like this," she said, the clinical tone never fully breaking even as the words grew more explicit. "The lubrication response is accelerating. If I lower myself any further, the contact will become direct. I am considering whether to do so immediately or to continue edging both of us for additional data. Decisions of this nature are normally made with greater detachment. Currently, detachment is… difficult."

She paused, tail lashing once behind her with enough force to send a gust of air through the laboratory. Then she smiled — small, sharp, and completely in control.

"Trainer-kun. You are the first variable I am testing under these new physical conditions. That makes you uniquely valuable. It also means I have no intention of being gentle with the process. I want to know how long you can last while I explore every new sensation this body is giving me. I want to know how your voice changes when my full weight settles. I want to record the exact moment your resistance turns into something more useful."

The pressure increased again — slow, deliberate, inescapable. The heat between her thighs was now openly slick in places, the evidence of her rising arousal impossible to ignore even at this scale. Her voice remained steady, but the undercurrent of intense, focused desire was no longer hidden.

"We will proceed. You will stay between my legs. You will give me every reaction I require. And when I decide the first stage of data collection is complete, I will move on to the next without asking permission."

She settled more of her weight down, the dense, powerful muscle of her thighs and the heavy curve of her ass beginning to fully enclose the space around the Trainer. The laboratory trembled under the careful, controlled application of 230 meters of newly enhanced body.

"Begin providing readings, Guinea Pig-kun. I am already far more interested in this experiment than I anticipated… and I have no intention of stopping until I am satisfied with the results."

The Trainer woke to the sensation of being completely enclosed.

There was no gradual return to consciousness. One moment there was the vague memory of falling asleep on the reinforced observation platform Tachyon had designated as “temporary subject housing.” The next moment the world consisted of heat, pressure, and the overwhelming reality of dense, living muscle. Agnes Tachyon’s colossal body was already positioned over them. Her 230-meter frame had lowered with careful, deliberate precision while they slept. The thick, heavily muscled thighs that had previously only trapped them now straddled their body completely. The heavy, solid weight of her ass and the hot, slick entrance of her pussy were already pressed down, the tip of the Trainer’s cock resting against the entrance of a cunt that could have swallowed a small vehicle.

She had not asked. She had not woken them. She had simply begun the next phase of the experiment.

Tachyon looked down from her impossible height, reddish-brown eyes half-lidded with focus and open arousal. A faint flush colored her cheeks. Her short brown hair was slightly more disordered than usual. The yellow sweater had been pushed up and out of the way, leaving the full, powerful lines of her lower body completely bare. Her tail hung low behind her, the fur still standing on end in irregular waves. Every slow breath she took made the massive walls of her thighs flex and settle more firmly around the Trainer’s body.

"You are awake. Good." Her voice was calm, almost conversational, despite the fact that she was already lowering herself another fraction, the slick, scorching heat of her pussy beginning to take the head of the Trainer’s cock inside. "I calculated that initiating the primary insertion phase during your sleep cycle would reduce initial resistance variables and allow for cleaner baseline data. The hypothesis appears correct. You are already inside me."

She sank down further. The stretch was extreme even for her new scale — the Trainer’s cock disappearing slowly into the tight, wet, scorching passage of a 230-meter Umamusume whose body had never taken a human like this before. Tachyon’s breath caught for the first time. A low, involuntary sound left her throat as more of the length was forced inside her. The walls of her cunt clenched in slow, experimental waves, testing the shape and heat of the intrusion.

"Fascinating…" She spoke through the sensation, still trying to maintain scientific detachment even as her hips gave a small, instinctive roll. "The sensory feedback is far more intense than the previous compression tests. Internal temperature is elevated. Muscle response along the vaginal canal is stronger than projected. And the psychological component — the knowledge that I began this while you were unconscious — is producing a measurable spike in my own arousal metrics."

She continued the descent without pause. Centimeter by impossible centimeter the Trainer was taken deeper, the thick, powerful muscles of her thighs and the heavy weight of her body leaving no possibility of escape or even significant movement. When she finally settled fully, the Trainer’s cock was buried to the hilt inside her, completely enclosed by the scorching, wet, ridiculously tight heat of her newly enhanced body. Tachyon remained still for several long seconds, simply feeling the data, her massive chest rising and falling with deeper breaths.

"Primary insertion complete," she announced, voice slightly rougher than before. "I am now going to test sustained riding under full body weight. The secondary objective of this session is conception viability."

She began to move.

The first roll of her hips was slow, experimental, and devastating. The dense muscle of her thighs flexed, lifting her just enough to drag the Trainer’s cock along the slick inner walls before she sank back down with controlled force. The wet sound of the connection was loud in the laboratory. A visible tremor ran through her colossal frame. Her tail lashed once, hard enough to send another gust of air through the room.

"I have been running theoretical models on cross-species reproductive compatibility since the scaling side-effect manifested," she continued, still riding in that same deliberate, grinding rhythm. "Umamusume reproductive systems are robust. Human genetic material is… adequate for testing. I want to know if impregnation is possible under these new physical parameters. Therefore I will be taking every drop you produce tonight. Multiple samples if necessary. You will not be permitted to pull out. You will not be permitted to finish outside. Every orgasm you have will be delivered directly into my womb for analysis."

Her pace increased. The heavy, powerful movements of her hips became more confident as she mapped the new sensations. Each downward stroke buried the Trainer completely inside her again, the tight, scorching walls milking along the length with deliberate intent. The sheer weight of her body made every thrust feel final. There was no leverage left for the Trainer. They were simply there to be used as the living instrument of her experiment.

"Your heart rate is elevated. Muscle tension is increasing. Pre-ejaculatory fluid is already detectable," she observed, looking down with open, scientific hunger mixed with raw lust. "Good. Continue providing data. Struggle if you wish. The resistance only improves the internal stimulation. I can feel every twitch. Every pulse. Every attempt to move is simply additional feedback for me to process while I fuck you."

She leaned forward slightly, resting more of her upper-body weight through her arms while her lower body continued its relentless, dominant rhythm. The yellow sweater hung loosely around her. Her reddish-brown eyes never left the Trainer’s face. The wet, filthy sounds of her cunt taking the cock over and over filled the reinforced laboratory, mixed with the low creaking of the structure under her controlled movements and the increasingly unsteady sound of her own breathing.

"I am already close to my first peak," she admitted, the clinical tone finally fraying at the edges. "The combination of absolute physical control, the novelty of this body, and the knowledge that I am actively attempting to breed a human subject is producing stronger results than anticipated. When I cum, the contractions will be intense. You will feel them. You will be forced to finish inside me by the strength of those contractions if you have not already. That is the intended outcome."

Her hips moved faster, heavier, more demanding. The thick, muscular thighs flexed with every rise and fall. The heavy ass slapped down against the Trainer’s hips with increasing force. Slick poured down around the connection, coating everything. Tachyon’s voice had dropped into a lower, hungrier register even as she continued narrating.

"Morumotto-kun. You are currently serving as both measurement instrument and potential genetic donor. I will not stop until I have taken at least one full sample. Preferably more. The experiment requires volume. It requires depth. It requires that you remain buried inside me while I use your body to test whether this new form is capable of carrying a hybrid result."

She slammed down particularly hard, grinding her clit against the Trainer’s body as she took every last centimeter again. A sharp, involuntary moan escaped her. The walls of her cunt clenched in a long, powerful wave.

"Data collection is proceeding better than expected," she managed, still riding, still dominating, still completely in control even as her own orgasm approached. "Continue. Give me everything. I will extract every drop myself if necessary. This body is mine to experiment with. Your cock is currently part of that experiment. And I have no intention of ending the session until I am thoroughly, measurably satisfied with the results… and thoroughly filled."

The laboratory trembled under the steady, powerful rhythm of a 230-meter mad scientist claiming her guinea pig for the first time, riding him with open dominance and explicit reproductive intent while the night continued outside, completely unaware of the experiment taking place within the reinforced walls.