The rooftop was silent except for the rhythm of his breathing. Jin Suho wiped the sweat from his brow and opened the glowing interface again. The system mocked him with its simplicity:
[Jin Suho]
Class: Shadow Assassin (Tier E)
Strength: 5
Agility: 6
Endurance: 4
Intelligence: 25
Perception: 7
Luck: 3
He stared at the numbers like a scientist dissecting a failed experiment. No, not failed. Incomplete. A formula missing its final variables.
Recording Session 01
Objective: Transform Tier E physical stats into sustainable combat readiness.Method: Application of progressive overload, aerobic/anaerobic conditioning, and statistical tracking.Tools: Bodyweight only. Mathematical modeling. Observation.
Suho sat cross-legged, his tone clinical as he spoke to himself. "Strength equals force over distance. Force is directly proportional to muscle cross-sectional area. If my current maximum push-ups are fifteen, then my muscular endurance corresponds to an output of roughly 60% of an average hunter recruit. If I increase this by two repetitions per day, then by Day 30, the projected maximum will be 75 push-ups. That's a 400% increase."
He lay flat and began his test.
Push-Up Trial
Set 1: 15 reps → failure at 16.
Set 2: 8 reps → failure at 9.
Set 3: 5 reps → complete muscular collapse.
Average heart rate: 172 bpm.Time to recovery (HR back to 100 bpm): 3 minutes, 12 seconds.Observation: Extremely poor endurance. Arms tremble, stabilizers weak. Chest strength minimal.
He pushed himself back into a sitting position, recording in his mind."ATP depletion consistent with untrained individual. Lactic acid accumulation noticeable at rep 10. Micro-tears confirmed by localized burning sensation. Tomorrow, expect delayed onset muscle soreness lasting 24–48 hours. Adaptation inevitable if progressive stress is maintained."
Squat Trial
He stood, inhaled deeply, and began squats.
Set 1: 20 reps → burning sensation at quads and glutes.
Set 2: 12 reps → significant instability, knees trembling.
Set 3: 9 reps → collapse to ground.
Estimated caloric burn: 90 kcal.Heart rate peaked: 165 bpm.Recovery: 2 minutes, 44 seconds.
"Lower body comparatively stronger than upper body, but balance is unstable. Micro-tears again. Growth expected. Strength is a function of stress plus nutrition. Nutrition is lacking."
Running Simulation
The rooftop wasn't large, but it was enough. He calculated the perimeter: 43 meters.One lap = 43 m.Stride length = 0.7 m.Steps per lap ≈ 61.
He started running.
Lap 1: 43 m, HR 140 bpm.
Lap 2: 86 m, HR 160 bpm.
Lap 3: 129 m, HR 178 bpm → collapse.
Distance covered: 129 m.Oxygen debt severe. Recovery: nearly 5 minutes.
Suho coughed, chest burning, but his lips curled faintly. "Aerobic capacity laughable. But that means potential gains are exponential. A weak baseline ensures massive improvement with proper overload."
Statistical Projection
Strength: 5 → projectable increase to 12 within 3 months.
Endurance: 4 → projected increase to 10 within 2 months.
Agility: 6 → requires plyometric and balance training. Estimated growth slower.
Intelligence: 25 → untouchable advantage. Must be leveraged.
"Formula is simple. Pain multiplied by repetition equals growth. Input energy, output strength. No miracles. Just science."
Scientific Notes
He leaned back against the railing, thinking aloud:
"Hypertrophy occurs when fibers repair. Key is progressive overload: gradually increasing resistance. Without weights, I'll maximize reps. Muscle responds to relative intensity, not equipment. Oxygen uptake must increase. Current VO2 max estimated at 32 ml/kg/min, below civilian average. Hunters average 55+. My target: 60. Method: interval running, 1:1 work-to-rest ratio."
His breathing steadied. Numbers formed invisible graphs before his eyes.
Push-up capacity graph: upward curve expected.
Running distance: linear growth with exponential aerobic adaptation.
Squat endurance: stabilizer strength limiting factor.
He chuckled softly, though his face remained cold. "Others see weakness. I see variables waiting to be rearranged."
The Equation of Survival
He stared again at the blue system screen. The cold numbers glowed.
Strength: 5.Endurance: 4.Agility: 6.
"Pathetic," he whispered. "But numbers don't lie. And numbers can change. Formula: Weakness + Discipline × Time = Power. No shortcut, no miracles, only mathematics."
His hands clenched into fists, veins standing out against pale skin. Pain surged through his arms, but he welcomed it. Each sting was confirmation. Each tremor was progress.
"Day one complete," he muttered, collapsing flat onto the rooftop. His chest rose and fell like a piston, but his eyes gleamed with ruthless clarity.
The city below glittered with hunter guild banners and neon advertisements of legendary warriors. None of them mattered. He had written the first line of his formula.
The rooftop was silent except for the low hum of neon signs flickering in the distance. Jin Suho stood still, breathing evenly, as if he were about to begin a delicate experiment rather than a physical drill. His body ached from yesterday's training, the soreness lingering in his arms and legs like burning wires, but his mind was sharper than any blade. Strength could be built slowly through repetitive stress, but speed, stealth, and precision—the essence of an Assassin—demanded geometry, biology, and physics.
He crouched low, analyzing the tension in his thighs and calves. The Assassin class was mocked as weak because it lacked raw force, but Suho had already concluded that efficiency could compensate for absence of brute power. Every movement would be reduced to numbers, every step a variable in an equation.
He marked ten meters across the rooftop using chalk lines he had scavenged from a broken brick. That would be his baseline for speed testing. A dagger in his hand felt heavier than it should, its balance imperfect, but that too was data. He placed a pebble at the far end of the line, the target of his first experiment.
"Trial one," he muttered, lowering his stance. His center of gravity dropped, knees bent at thirty-five degrees, spine tilted forward. He calculated in his head—at a forty-five degree lean, maximum acceleration could be achieved by redirecting vertical force into horizontal thrust. He pushed off.
His feet slapped against the rooftop as he sprinted, legs pumping but lacking explosive power. The pebble loomed closer. He tapped it after 2.4 seconds, then skidded to a halt, chest rising and falling.
Velocity equals distance over time. Ten meters divided by 2.4 gave him 4.16 meters per second. He scowled. Pathetic compared to trained hunters, whose averages exceeded 8 m/s. But data was data.
"Acceleration slow. Push-off weak. Stride length uneven. Improvement necessary."
He reset and tried again. This time, he leaned further forward, arms swinging more aggressively. The pebble was reached in 2.2 seconds. Velocity: 4.54 m/s. A small increase, but statistically significant. Posture adjustment alone yielded nearly 10% improvement. He repeated the drill five times, recording mental notes: stride length averaging 0.72 m, steps per ten meters between 13 and 14, heart rate peaking at 156 bpm. Sweat slicked his hair, but his eyes remained cold, detached, calculating.
Speed, however, was only one component. Stealth required silence, and silence was a science of sound.
Suho crouched again, this time focusing on his foot placement. He experimented with heel-to-toe walking, then toe-first contact. Heel-to-toe produced a dull slap, reverberating faintly in the still night. Toe-first, with knees bent to absorb shock, produced significantly less noise. He measured it by feel, but approximated decibel reduction at 30–40%. Not precise, but enough to note.
"Sound intensity proportional to impact force. Lowering vertical displacement reduces amplitude. Equation: less bounce equals less noise."
He practiced moving across the rooftop, each step calculated: knees at forty-five degrees, weight distribution 60% front, 40% rear, torso compressed. His silhouette shrank against the dim railing. In his mind, he mapped the field of vision of a human opponent—190 degrees peripheral, with a thirty-degree blind cone behind. Optimal entry: 25 degrees off-center, maintaining low posture. By repeating the simulation, he moved smoother, quieter, until he could traverse the length of the rooftop with almost no sound at all.
Geometry was next. An Assassin could not always approach directly. Straight lines were fast but predictable. He drew patterns in chalk, triangles and arcs, then ran them repeatedly. A forty-five degree angle produced efficient approach speed while keeping his profile narrow. Ninety degrees allowed for flanking but slowed his advance. One hundred and twenty degrees to the rear created maximum safety but demanded energy. He logged the variables like formulas etched in stone.
The dagger training followed. He held the blade up, studying its reflection in the moonlight. His hand trembled slightly from fatigue, but his mind was steady. He slashed horizontally, timing himself—0.9 seconds per strike. The force spread wide, wasting energy. He adjusted to diagonal, forty-five degrees. 0.8 seconds, sharper penetration path. Then he thrust, straight and clean. 0.6 seconds. The fastest, most efficient motion with minimal wasted force.
"Data confirms. Thrust optimal for low-strength users. Smaller surface area contact equals deeper penetration. Slashes require strength to amplify trauma. My class lacks strength. Therefore, thrust becomes primary attack."
He practiced thrusts repeatedly, arm snapping forward like a piston, withdrawing instantly. Each repetition was logged in his head, every angle and trajectory memorized. He simulated striking vital points—neck, heart, liver, arteries—calculating entry points at precise degrees. A seven-degree inward thrust angled under the ribs, targeting the heart. A sixteen-degree upward thrust could pierce the subclavian artery. Numbers replaced instinct. His mind was his deadliest blade.
Hours passed. His shirt clung to his body, soaked in sweat, muscles screaming for release. His legs quivered from crouching, his forearms burned from dagger repetition. Yet he did not stop until his notes were complete.
Sprint velocity: increased from 4.16 m/s to 4.54 m/s.
Stride efficiency: improved through lean posture.
Stealth efficiency: noise reduction by 40%.
Optimal entry angle: 25–45 degrees.
Dagger technique: thrust superior in 70% of combat scenarios.
His heart pounded at 170 bpm, his throat dry, but his eyes glittered with satisfaction. "Efficiency multiplier achieved. At strength 5, I must double effectiveness to compete. No wasted motion. No wasted energy."
Finally, he collapsed against the railing, chest heaving. Sweat dripped onto the cracked concrete below, each drop a marker of progress. Pain was irrelevant. What mattered was the equation he had begun to write:
Weak stats + perfect efficiency × relentless calculation = survival.
He whispered into the night, voice barely audible:"They mock Shadow Assassin as Tier E. But Tier E means nothing when geometry, physics, and biology become weapons. Even weakness can be optimized into perfection. And perfection kills."
The rooftop was silent again, save for the rhythm of his ragged breathing. But behind his exhaustion lay a razor edge of determination. This was not training—it was data collection. Each step, each cut, each calculation brought him closer to rewriting the world's equation.
And Jin Suho would not stop until every number obeyed him.
The small apartment was silent except for the ticking of an old clock on the wall. Jin Suho sat cross-legged on the floor, sweat still dripping from the assassin drills he had performed hours ago. His body was sore, every fiber of his muscles trembling as though screaming at him to stop, yet his mind was sharper than ever. He pulled up the translucent blue panel that floated in the air.
[ Status Window ]Name: Jin SuhoClass: Shadow Assassin (E-rank)Level: 2Strength: 6Agility: 9Endurance: 7Dexterity: 7Intelligence: 12
He stared at it for a long moment, lips pressed into a thin line. The numbers were painfully low. After all the training he had forced himself through, only a single point or two had moved. His sweat and pain had bought him almost nothing.
He exhaled through his nose, mind racing as if he were working on a math problem. "I exerted close to ten thousand joules of work today, yet the increase in my Strength stat is effectively one point. That is not an efficient exchange of effort. At this rate, I'd need months—years even—before these stats resemble those of a real hunter."
His analysis reminded him of the physical principles he studied back in high school. Training produced hypertrophy: muscle fibers grew denser, mitochondria increased, the nervous system adapted to signal more efficiently. But the System was not bound to pure biology. It measured growth differently, with hidden formulas only it knew. Still, Suho believed any formula could be broken if studied long enough.
Just as he was about to close the panel, a sharp tone rang inside his head.
[Ding!]
A new window flashed.
[ Special Quest Unlocked: Path of Self-Forged Assassin ]Description: Your persistence in training has been acknowledged. To transcend limits, complete the following:– 1000 push-ups– 1000 squats– 1000 sit-ups– 1000 pull-upsTime Limit: 24 hoursReward: +10 Strength, +10 Agility, +10 Endurance, +10 DexterityFailure Penalty: -5 to all stats
Suho's eyes widened slightly. "A… quest? From training?"
He had heard of hunters receiving quests before. They were always tied to dungeons or monster extermination. Never something like this. No one had ever spoken of a system that demanded physical exercise in such absurd amounts. But the reward—forty total stat points—was worth more than gold. That was the equivalent of jumping several levels instantly, a growth no normal hunter could hope for in such a short time.
He accepted without hesitation.
[ Quest Accepted. ]
He placed his daggers aside. His battlefield would not be a dungeon tonight. It would be his own body.
He pressed his palms to the floor, sliding into the first position. His fingers spread wide for balance, spine aligned in a perfect plank. "Push-ups first. Each rep approximates seventy percent of my bodyweight. With a mass of sixty-two kilograms, that means I'm pressing forty-three kilograms per movement. Multiply by one thousand… forty-three thousand kilograms of cumulative load."
He lowered himself smoothly, arms bending until elbows reached ninety degrees. His chest hovered centimeters above the floor before he pushed back up. He inhaled on the descent, exhaled on the rise, keeping tempo like a metronome. Ten, twenty, thirty—the rhythm carried him at first.
At one hundred, a dull burn began spreading through his triceps. By two hundred, his chest was tight, breath heavier. He catalogued the sensations like data points: burning indicated lactic acid accumulation; trembling arms meant motor units were firing chaotically. Efficiency was dropping, but adaptation was beginning.
His mind calculated: each contraction required adenosine triphosphate, each ATP molecule storing about 7.3 kilocalories per mole. Anaerobic glycolysis was inefficient, yielding only two ATP per glucose molecule compared to thirty-six in aerobic respiration. That was why his muscles screamed for oxygen.
At five hundred push-ups, his arms shook violently. Sweat pooled beneath him, dripping from his chin in steady streams. He stopped, not to rest, but to re-evaluate. "Set partitioning. I'll divide into intervals of twenty with minimal recovery. Muscle fibers adapt faster under consistent overload."
He forced himself back into motion.
When his arms could no longer extend, he collapsed, panting on the floor. He pulled up the quest panel.
[ Push-ups: 700 / 1000 ]
He smirked weakly. "Seventy percent completed. Quadriceps next."
He stood, legs unsteady. Positioning his feet shoulder-width apart, he straightened his spine. "Squats engage quadriceps femoris, hamstrings, gluteus maximus. They are the engines of human locomotion. With each rep, ground reaction force exceeds six hundred newtons on the knee joint."
He sank down, thighs parallel to the floor, then pushed upward. One, two, three… Each squat felt like lowering and raising an invisible weight. By fifty, his legs began to quake. At one hundred, he tasted iron in his mouth. At two hundred, his lungs burned like fire.
He calculated again to keep himself sane: "Body mass multiplied by gravity, distributed across two legs. Each repetition approximately six hundred newtons. Multiply by one thousand reps equals six hundred thousand newtons. Equivalent to supporting the weight of a compact car through my knees."
When his legs gave out, he collapsed backward, breathing ragged. His quest window updated.
[ Squats: 500 / 1000 ]
He laughed dryly. "Halfway."
Without delay, he moved to the next. He lay down flat, bent knees, crossed fingers at his temples. "Sit-ups target rectus abdominis, but the true stabilizers are iliopsoas and transverse abdominis. If I lose form, stress transfers to lumbar vertebrae."
He curled upward, elbows brushing knees, then lowered himself. Over and over. He counted silently, mind drifting to biochemical cycles. Each contraction required calcium ions released into sarcoplasm, binding to troponin, allowing actin and myosin filaments to slide. When calcium depleted, contraction ceased.
By two hundred sit-ups, his abdominal wall was on fire. At three hundred, his vision blurred. At four hundred, every breath felt like inhaling broken glass. But he continued, body moving like a machine driven by sheer calculation.
Quest window updated again.
[ Sit-ups: 300 / 1000 ]
"Not enough. Still far."
Finally, he gripped the steel bar wedged in his apartment doorway. His palms burned as he pulled himself up. "Pull-ups. Vertical displacement of total body mass. Each rep equals sixty-two kilograms lifted. One thousand reps equals sixty-two thousand kilograms—lifting the weight of a military tank cumulatively."
He pulled. Chin over the bar, then lowered. Again. Again. By ten, his arms screamed. By thirty, his grip faltered. By fifty, blisters tore on his skin, blood smearing the metal. He adjusted grip to distribute force differently, using kipping motions to cheat momentum. His arms were no longer his own; they belonged to instinct and stubborn will.
Quest update.
[ Pull-ups: 120 / 1000 ]
Hours blurred. His body cycled between burning, numbness, and unbearable heaviness. He rationed water, used isometric stretches between sets, and recited formulas in his head to drown the pain. Oxygen debt, glycogen depletion, lactate threshold—every scientific principle became a mantra.
When dawn painted the sky pale gray, he collapsed to the floor. His body trembled uncontrollably, but his quest panel gleamed before his eyes.
[ Push-ups: 1000 / 1000 ][ Squats: 1000 / 1000 ][ Sit-ups: 1000 / 1000 ][ Pull-ups: 1000 / 1000 ]
[ Ding! Quest Completed. ]Reward applied.
[ Status Updated ]Strength: 6 → 16Agility: 9 → 19Endurance: 7 → 17Dexterity: 7 → 17
Warmth surged through his body like liquid fire. It wasn't ordinary muscle fatigue recovery; it was the System itself rewriting his physiology. His fast-twitch fibers felt denser, his nervous reflexes sharper, his core like steel. Even his heartbeat steadied, strong and efficient like a trained athlete's.
He lay flat on the floor, drenched in sweat, chest rising and falling like a bellows. A faint grin crept onto his exhausted face. "So the System does recognize calculated effort. Science and numbers… they are my weapons. If one quest can push me this far, then I'll rewrite the entire formula of strength."
His eyelids closed. The city outside awoke, but inside the small apartment, a boy once abandoned by family and mocked by peers had just taken his first step toward rewriting destiny.
The air inside the cramped apartment was still, heavy with the lingering smell of sweat. Jin Suho lay motionless for several minutes, staring at the ceiling. His body should have been broken—muscles torn, joints inflamed, tendons screaming for rest. The cumulative stress of four thousand repetitions should have left him immobilized for days. Yet when he inhaled deeply, his lungs expanded effortlessly. His chest was light. His arms felt powerful, not sore. His legs, instead of cramping, thrummed with hidden strength.
He sat up slowly. No dizziness, no fatigue. The burning ache that had consumed him hours ago was gone, replaced by clarity. His pulse was steady at around forty-five beats per minute—astonishingly low for someone his age, a sign of extreme cardiovascular efficiency.
"This… isn't normal biological recovery," he muttered, narrowing his eyes. "This is a physiological reset. The System didn't just grant me stats—it recalibrated my body entirely."
He analyzed out loud, as though recording a lab report:
"Normal hypertrophy requires microtears in muscle fibers, followed by protein synthesis during rest. Recovery time ranges from forty-eight to seventy-two hours, depending on muscle group and intensity. But in my case, the System bypassed the biological timeline. It induced an immediate adaptation, essentially rewriting cellular structures. Mitochondrial density, capillary networks, sarcomere alignment—all of it has been recalibrated in real-time. That explains the absence of pain."
He clenched his fists, marveling at the sensation of energy flowing through his veins. He jumped to his feet in a smooth motion, lighter than he had ever felt.
"Agility increase by ten points. Endurance increase by ten. If the System is linear, that means my reaction time, stamina, and speed are amplified by at least one and a half to two times baseline human maximum. But let's quantify."
He took a stance, legs shoulder-width apart, dagger in his right hand. His movements felt precise, clean, as though invisible wires guided his body into optimal alignment. He performed a standard Assassin skill drill: step forward, low crouch, slash, retreat.
Whoosh. The blade cut the air with a sharp whistle.
"Lighter," he whispered. "The coefficient of friction between muscle contraction and motion has been reduced. Efficiency is higher. Every strike consumes less energy while producing greater velocity."
He set the dagger on the floor and began sketching invisible equations in the air with his finger.
"Let's calculate attack velocity. Assume my arm length is 0.72 meters. If my reaction time has decreased by forty percent and muscle contraction speed increased by sixty percent, then the angular velocity of my arm swing is approximately doubled. Baseline swing speed for an untrained human is 6–8 meters per second. With the stats increase, I should be hitting around 15–16 meters per second."
He picked up the dagger again and slashed downward, then diagonally. The air displacement was audible. He measured by ear and vibration. "Approximately correct."
He crouched, then dashed forward to simulate closing the gap on an enemy. The distance across the apartment was five meters. His feet barely made sound against the floor as his body blurred forward. He covered the distance in less than a second.
"Five meters in 0.8 seconds. That's 6.25 meters per second sprint speed. Olympic sprinters average 10 meters per second at peak, but that requires full-body acceleration. I achieved this indoors, starting from static stance, with minimal effort."
His lips curved slightly. "Agility stat isn't just raw speed. It's balance, motor control, neuromuscular efficiency. The System integrated biomechanical optimization into my physiology."
He rotated the dagger in his palm, feeling the shift of weight. Normally, a weapon felt like an extension of the hand only after hundreds of hours of practice. But now, the blade obeyed his smallest twitch.
He visualized a monster. From the books he had read, low-tier dungeon beasts—horned wolves, shadow lizards—had average movement speeds of 12–15 meters per second and attack angles within 30–60 degrees. Their lunges were predictable but lethal for a novice hunter.
He adjusted his stance, shoulders relaxed, dagger near his hip. His mind simulated the encounter.
"If a wolf lunges at 14 meters per second from 3 meters away, time to impact is 0.21 seconds. My reaction time, at 120 milliseconds baseline reduced by 40%, is now around 70 milliseconds. That gives me a margin of 0.14 seconds to reposition and counter."
He shifted weight onto his back foot, testing. "In that window, I can sidestep 0.5 meters laterally, rotate torso by thirty degrees, and execute a slash upward across the jugular. Blade travel time at 15 meters per second for 0.72 meters of arc length equals 0.048 seconds. Total sequence: dodge and counter in 0.188 seconds. Just within the margin."
He repeated the motion physically: a sudden sidestep to the left, body twisting, dagger snapping upward in a lethal arc. The strike cut through empty air, but Suho could almost see the imaginary wolf collapsing at his feet.
His breathing remained calm, steady, as though his body was finally in harmony with the scenarios his mind had always been able to calculate.
"Before, I only had the math. Now, I have the body to match it."
He moved to the window, gazing out at the city skyline. The streets were already alive with hunters preparing for expeditions. He imagined himself among them, dagger flashing, his brain calculating every angle and trajectory, his body executing with mechanical precision.
He closed his eyes and ran the numbers again.
"Optimal positioning: maintain distance at 1.8 meters, the threshold where lunging predators cannot generate full acceleration before impact. Attack vectors: 30 degrees from the enemy's blind spot maximizes strike efficiency. Probability of first-hit kill with current stats: 67%. Margin of error reduced by dagger sharpness and armor penetration."
He tightened his grip on the weapon. The dagger felt alive, pulsing with hidden potential. He swung again, faster this time, the blade a blur.
The sound echoed like a promise.
"I can kill a monster now."
His voice was quiet, almost clinical, but beneath it was a spark of something fierce. For the first time since receiving the cursed E-rank class, he felt genuine possibility. He was still a Shadow Assassin, mocked and despised. But if numbers never lied, then Jin Suho had already rewritten the rules.
The System had given him a path—one no one else seemed to know. Through science, through precision, through sheer calculation, he would turn the weakest class into the sharpest blade.
He looked down at his reflection in the dagger's polished surface. His green eyes burned with new clarity, framed by the comma-styled fringe of his short red hair.
"Now… let's test this formula against reality."