Inside the U.A. support development lab, Izuku Midoriya sat at one of the workbenches. He had his chin resting on one hand and stared blankly into space while his other hand drummed unconsciously against the metallic surface. His mind was a whirlwind of unanswered questions.
The stone armor Yu had developed. Her improved scale control. The way her body had reacted during that moment. And then there was the other thing, something he had noticed himself but did not quite understand: the way the steel bar had bent in his hands without causing him the slightest bit of pain. Normally, striking steel with your bare hands left you with bleeding knuckles. But he had felt nothing. Not even a tingle.
Was it an energy transfer? Or is my Quirk evolving too? he muttered to himself, frowning.
The problem was that he did not have enough data. His Quirk, Train, had been a mystery for years. First he thought it was useless, then he discovered it worked on dogs, and finally it revealed its true potential: optimizing human bodies. But every new discovery generated ten more questions. It was like trying to solve a puzzle when someone kept adding new pieces every five minutes.
And then there was Yu. The way she had looked that morning in the kitchen, desperately trying to maintain her professional composure while her face flushed every time their eyes met. She was adorable. But she was also a problem. He could not concentrate on the scientific aspect of his Quirk when half of his brain was busy remembering the touch of her skin transforming into stone under his fingers.
I need help, Izuku told himself in a low voice. I need someone who can see this from an objective angle. Someone who understands biology, Quirk physics, and who won't get distracted by...
"Izuku? Are you okay?"
The female voice snapped him out of his trance. Izuku looked up and blinked.
Melissa Shield stood in front of him with an expression of genuine concern on her face. She wore her usual white lab coat, unbuttoned over a light blue blouse that fit her figure in a way that could only be described as professionally distracting. Her blonde hair was pulled back into a high ponytail, and she had a grease smudge on her left cheek, likely from working on some prototype.
"Melissa," Izuku said, straightening up quickly. "I didn't hear you come in."
"That is obvious," she replied with a small smile, crossing her arms. The gesture made her blouse tighten in a way that Izuku definitely should not be noticing right now. "You have been sitting there like a statue for the last fifteen minutes. I saw you from my workstation and thought maybe you had fallen asleep with your eyes open."
"I was just... thinking."
"Thinking very intensely, it seems." Melissa approached and sat on the bench across from him, leaning slightly forward. "Does it have something to do with your Quirk? I know you have been doing research on your own lately."
Izuku opened his mouth to respond, but in that moment, his eyes completely betrayed his brain. His gaze dropped involuntarily toward Melissa's neckline. It was not his fault, really. It was just that Melissa's blouse, combined with the way she had leaned in, created a direct line of sight.
"Izuku?" Melissa asked, tilting her head with curiosity.
"Yes! Yes, exactly, my Quirk," Izuku responded quickly, forcing himself to look directly into Melissa's eyes. Green eyes. He had to focus on the green eyes. "I am trying to understand some recent evolutions. There have been changes I cannot fully explain on my own."
Melissa smiled enthusiastically. "That sounds fascinating! You know I love this kind of analysis. What kind of changes?"
Izuku hesitated. How was he going to explain this without mentioning Yu? Without mentioning the night they had spent together? Without mentioning that his Quirk seemed to activate in completely new ways during intimate situations?
But as he thought about that, his gaze drifted again. This time it was a kind of subconscious recognition. Izuku's eyes landed on Melissa's chest again, and this time, something clicked in his brain.
Breasts.
Yu has large breasts. The armor appeared during sex. My Quirk reacts to intimate physical contact. Melissa has large breasts. Melissa is a genius. Melissa can analyze data without emotional judgments. Melissa could be the key to understanding all of this.
It was as if all the pieces of the puzzle had suddenly fallen into place. The answer had been right in front of him the entire time, literally. He needed someone with world-class scientific intelligence who could help him decipher the variables of his Quirk. And Melissa Shield was likely the smartest girl he knew.
"Melissa," Izuku said suddenly, an expression of realization lighting up his face. "You are a genius."
Melissa blinked, surprised by the sudden change in his tone. "Well, thank you, but what exactly are we talking about?"
"You!" Izuku stood up with enthusiasm, nearly tripping over the bench in the process. "You can help me. You are the perfect person for this. You have knowledge of biomechanical engineering, Quirk physics, and you can analyze data without... without emotional complications."
"Emotional complications?" Melissa arched an eyebrow, but her smile widened. "Izuku, you are flattering me and scaring me at the same time. What exactly do you need me to do?"
Izuku took a deep breath. "I need you to help me understand how my Quirk works. I have discovered that Train can do more than just slightly optimize Quirks. It can trigger evolutions in other Quirks. But I don't fully understand the parameters."
Melissa leaned forward even further, clearly intrigued. "Evolutions in other Quirks? Izuku, that is incredible. Have you documented this?"
"Yes and no," Izuku admitted, rubbing the back of his neck. "I have a case study. But it is complicated. It involves another person. And before I share any information with you, I need her permission."
"Of course," Melissa nodded immediately. "Privacy in Quirk research is fundamental. Who is the person?"
Izuku swallowed hard. "Yu Takeyama. Mt. Lady."
Melissa's eyes went wide. "Mt. Lady? Your boss? Izuku, is she your study subject?"
"Well, it is complicated," Izuku explained. "I am her Quirk consultant. I have been helping her optimize her gigantification."
"That makes sense," Melissa said slowly, processing the information. "But you said there are evolutions. What kind of evolutions are we talking about?"
"Let me call her first," Izuku said, pulling out his phone. "I need her authorization before sharing the details."
Melissa nodded and leaned back on the bench, crossing her legs as she watched Izuku with curiosity. He dialed Yu's number and waited. The phone rang three times before she answered.
"Izuku," Yu's voice sounded surprised. "Did something happen? I am in the middle of a meeting with Midnight."
"I am sorry for interrupting," Izuku apologized quickly. "But I need to ask you something important. Can I speak with you in private for a moment?"
There was a pause, followed by the sound of footsteps and a door closing.
"Alright, I am alone," Yu said, and her voice now sounded softer, almost intimate. "What is it?"
Izuku took a deep breath. "Yu, I have been thinking about what happened. About the armor. About your improved scale control. And also about something I noticed in myself: an increased physical resistance that I cannot fully explain. I think my Quirk is evolving, and I think your Quirk did too because of our interaction."
"Izuku..." Yu's voice tensed slightly. He could imagine her biting her lip, her face flushing. "Where are you going with this?"
"I need help to understand the mechanisms," Izuku continued. "And I know someone who is probably the best person in all of Japan to analyze these kinds of phenomena: Melissa Shield. But before I share any information with her, I need your permission. I know it is personal, but I think if we can understand this scientifically..."
"Wait," Yu interrupted. "Melissa Shield?"
"Yes, her. She is brilliant, Yu. And she can help us."
There was a long silence on the other side of the line. Izuku could hear Yu's breathing, which was slightly accelerated. He knew what she was thinking. She was thinking about the embarrassment of another person knowing about their night together. She was thinking about the professional implications.
But then Yu spoke, and her voice was firm.
"Do it."
Izuku blinked, surprised. "Really?"
"Yes," Yu confirmed. "Look, Izuku, I am a professional hero. I have dealt with things much more embarrassing than this. And if what we discover can help you understand your Quirk, if it can help me be a better hero, then it is worth it. I am not going to let my pride or my shame stand in the way of something this important."
Izuku felt a surge of affection for her. "Yu, thank you. Truly."
"But," Yu added with a warning tone, "you better keep the graphic details to a minimum, understood? She doesn't need to know every detail of what happened in that bed. Only what is scientifically relevant."
"Of course," Izuku promised, suppressing a smile. "Only what is necessary."
"Good. Now let me get back to this meeting before Midnight starts asking uncomfortable questions. Let me know what you find out."
"I will. Thanks, Yu."
"You're welcome, Izuku. And hey..."
"Yes?"
"You are a good boy. Don't forget that."
The call ended. Izuku stared at the phone for a moment, feeling a warmth in his chest.
"Well?" Melissa asked, snapping him out of his daydream. "Do we have a green light?"
"We have a green light," Izuku confirmed, putting away the phone. "But we need to go somewhere more private for this. And we need Yu to come. Preferably to a lab that can handle her gigantification."
Melissa stood up, practically radiating enthusiasm. "I know the perfect place. Gym Gamma has measurement sensors and is reinforced for high-impact training. I can set up equipment there in twenty minutes. Can you get Mt. Lady to come?"
"I will send her a message," Izuku nodded. "But Melissa, before we start, there is something you need to know. The changes in Yu's Quirk... they happened during a situation of high physical intimacy. Very high. Like in... well."
Melissa's eyes went wide as she processed what Izuku was hinting at. "Oh. Oh. I see."
"Yes."
"So you and Mt. Lady..."
"Yes."
Melissa blinked several times, her face moving through a series of expressions ranging from surprise to realization and finally to a kind of professional determination. "It is fine. It is fine, I can work with that. It is just another factor in the equation. It is no different than any other physiological stimulus."
"Are you sure you are comfortable with this?" Izuku asked, studying her face.
"Izuku," Melissa said firmly, "I am a scientist. I have seen, measured, and analyzed things much more uncomfortable than this. Besides," she added with a small mischievous smile, "it is not like I am going to ask you to recreate the experiment in front of me. We just need the data."
"Right. Just the data."
"Then let's go get that data."
An hour later, Izuku stood in the center of Gym Gamma, surrounded by an impressive amount of scientific equipment that Melissa had transported and set up with an efficiency that bordered on superhuman. There were motion sensors, thermal cameras, density meters, electromagnetic field scanners, and what appeared to be some kind of Quirk energy spectrometer.
"Is all of this necessary?" Izuku asked, watching the cables stretching across the floor like snakes.
"If we want complete data, yes," Melissa replied, adjusting something on a tablet. "We don't know which variables are relevant yet, so we are going to measure everything. Body temperature, heart rate, energy emissions, changes in molecular density, electromagnetic fields... everything."
"I feel like a middle school science experiment."
"Technically you are," Melissa smiled. "But a very interesting experiment."
The gym door opened and Yu Takeyama walked in. She wore her hero costume, the skin-tight purple outfit with white details that left little to the imagination. Her heeled boots clicked against the floor as she walked toward them with her characteristic professional model stride. But Izuku could see the slight tension in her shoulders and the way her eyes avoided Melissa's.
"Hello," Yu greeted in a professional voice. "It is a pleasure to see you again, Melissa Shield. I am sorry for taking your time with these kinds of things."
"It is not a waste of time, on the contrary, it is something I am extremely interested in," Melissa replied, shaking Yu's hand. "And please, call me Melissa. Izuku has told me a bit about the evolution of your Quirk. It sounds absolutely fascinating."
Yu shot a quick glance at Izuku, who nodded subtly. She sighed, relaxing her shoulders slightly. "Yes, well, fascinating is one word. Completely unexpected and slightly terrifying would be more accurate."
"The best Quirk evolutions usually are," Melissa commented with a reassuring smile. "Ready to begin?"
Yu looked around, evaluating the equipment. "What exactly are we going to do?"
"First, we are going to establish a baseline," Melissa explained, gesturing toward a marked area on the floor. "I want measurements of your Quirk in its normal state. Then, we are going to try to recreate the conditions that produced the evolution. Izuku mentioned that it involved direct physical contact with him while you were using your gigantification."
"Correct," Yu confirmed, her face flushing slightly. "He was... in contact with me when my skin changed."
"Then we will start with that," Melissa nodded, without losing her professionalism. "Yu, can you activate your gigantification first? I want to see the normal readings."
Yu took a deep breath and nodded. She moved to the center of the marked area and closed her eyes. A moment later, her body began to grow. The transformation was impressive even after seeing it several times. Her limbs lengthened, her torso expanded, and her hair seemed to flow upward as her height skyrocketed. In a matter of seconds, she was standing at her full twenty meters, her head nearly touching the high ceiling of the gym.
"Incredible," Melissa whispered, watching the readings on her tablet. "The amount of energy required for this transformation is astronomical. And the speed... less than three seconds for a complete mass change."
"It's exhausting," Yu admitted from above, her voice booming slightly. "Normally, gigantification tends to tire me out a bit."
"But Izuku mentioned that you developed better control," Melissa said, making notes. "Can you demonstrate that?"
Yu nodded. She closed her eyes again, and this time, her body began to shrink, stopping at approximately three meters tall, exactly double her normal height.
"Here," Yu said, opening her eyes. "This is the midpoint I have been practicing."
"Fascinating," Melissa murmured, walking around Yu while observing the readings. "Your density in this form is significantly higher than it should be proportionally. It is as if your mass is not decreasing linearly with your size."
"That was one of the things I noticed," Izuku intervened. "When she is at this size, she is much heavier and stronger than expected."
"Which suggests that your Quirk is compressing mass instead of just scaling it," Melissa reasoned. "That is revolutionary, Yu. Normally, size Quirks maintain a constant proportion. Yours is breaking that rule."
Yu smiled, feeling visibly pleased by the professional analysis. "Izuku said the same thing. But there is more."
"The armor," Melissa guessed.
"The armor," Yu confirmed.
"Alright," Melissa returned to her tablet. "Izuku, I need you to approach Yu. Maintain physical contact with her, preferably in an area of high nerve concentration. The arms or hands would be ideal to start."
Izuku nodded and stepped closer. Yu crouched slightly, extending her arm. Even in her reduced form, her hand was significantly larger than Izuku's. He took it with both hands, feeling the warm, soft skin under his fingers.
"Now," Melissa continued, "Yu, I want you to focus on the sensation you had when the armor first appeared. You don't need to recreate the exact circumstances," she added quickly, noticing the blush on Yu's face, "just the underlying emotion."
Yu closed her eyes, breathing deeply. Izuku could feel her pulse racing under his fingers. Several seconds passed. Nothing.
"Maybe it is different now that Melissa is here. It breaks the moment of intimacy and therefore your body refuses to cooperate," Izuku commented. "In that moment, I was in contact with more areas of her body and there was a bit more intimacy."
"True," Melissa nodded. "Yu, do you feel comfortable with Izuku maintaining contact with other areas? Just for testing purposes."
Yu opened one eye, looking at Melissa with a mix of embarrassment and determination. "Go ahead."
Izuku moved his hand up Yu's arm, feeling the toned muscles under the skin. Then he placed his other hand on her shoulder. The contact was different now that there was context. There was an implicit intimacy that neither of them could completely ignore.
And then it happened.
A grayish glow began to spread from where Izuku's hands touched Yu's skin. Like ink in water, the color spread across her arm, transforming the texture of her skin. In a matter of seconds, her entire arm was covered by the stone armor.
"There it is!" Melissa exclaimed, nearly dropping her tablet in excitement. "The sensors are going crazy! Yu, how do you feel?"
"Heavy," Yu replied, lifting her armored arm. "But strong. Like I could crush steel without thinking twice."
"Let's test that," Melissa said, pointing to a steel training bar on the floor. "Try to bend it with your armored hand."
Yu picked up the bar with her transformed hand. She squeezed it. The steel groaned, then bent as if it were playdough. Yu dropped it with a metallic clang.
"Incredible," Melissa sighed. "Izuku, can you maintain the contact? I want to see if the armor spreads."
Izuku nodded. He moved his hands toward Yu's neck, touching the soft skin of her throat. The transformation continued, spreading across her neck, her jaw, and starting to climb up her face.
"It is following the contact," Melissa observed, making notes frantically. "It is as if your Quirk is programming her body to respond defensively to your touch, Izuku."
"But why?" Izuku asked, fascinated by the process. "Why would my touch trigger a defensive response?"
"Because your Quirk is optimization," Melissa replied, looking up from her tablet. "You don't just optimize muscles, Izuku. You optimize complete bodily systems. And when you are in intimate contact with someone, especially in situations of high emotional and physical intensity, your Quirk interprets that person's body's needs and satisfies them."
Izuku blinked, processing the information. So when Yu and I... when we were together, her body needed protection. It needed to be more resistant to handle the physical intensity of the moment.
"Exactly," Melissa confirmed. "And your Quirk responded by creating an evolutionary adaptation in hers. It's brilliant, Izuku. It is as if your Quirk is a real-time biological engineer."
Yu let out a sigh, her face now partially covered by the stone armor. "So basically, my sex life accidentally gave me superpowers."
Melissa could not help but laugh at that. "When you put it that way, it sounds like the plot of a bad science fiction movie."
"Welcome to my life," Yu replied with a tired smile.
Over the next thirty minutes, they continued the tests. Melissa measured the density of the armor, its thermal conductivity, and its impact resistance. They discovered that the armor could appear and disappear at Yu's will once it had been activated at least once, though it was easier to summon when Izuku was nearby. They also discovered that the armor did not cover her entire body uniformly; the areas that had received more direct contact from Izuku developed thicker protection.
"This raises an interesting question," Melissa said as Yu shrank back to her normal size, letting the armor fade away. "If your Quirk can trigger evolutions in other Quirks based on situational needs, what would happen with someone whose Quirk is already incredibly powerful?"
Izuku's eyes went wide. "Are you talking about One for All?"
"Well, yes, at least that is what I have in mind," Melissa answered, feeling slightly bold in her scientific argument.
Izuku's mind was already working at full speed. His eyes drifted involuntarily toward Melissa's chest again. Yu had an impressive physique and her Quirk had evolved dramatically. Melissa also had an impressive physique and a Quirk with untapped potential. The pattern was there, right in front of him.
"Melissa," Izuku said slowly, "if my Quirk could optimize yours in the same way it optimized Yu's... if it could unlock the full potential of your One for All just as my ancestor also said..."
"It would be revolutionary," Yu whispered. "It would completely change the battlefield."
Izuku took a step toward Melissa. She was standing by her workstation, the tablet still in her hands, looking at him with a mix of scientific curiosity and fear.
"For my Quirk to work at its peak," Izuku said carefully, "it needs direct physical contact. A lot of contact. With Yu, it worked because... well, because there was a lot of skin-to-skin contact."
Melissa swallowed hard, her face flushing slightly. "I understand."
"And based on the data we just collected," Izuku continued, feeling increasingly confident in his theory, "areas with a higher concentration of nerves respond better. Areas with a lot of adipose tissue and glands. Sensitive areas."
"Izuku," Yu interrupted from the other side of the gym, in a warning tone. "Where are you going with this?"
But Izuku was completely focused on Melissa now. On the way her green eyes looked at him with a mix of scientific anticipation and nervousness. On the way her chest rose and fell with every breath. On the fact that if his theory was correct, if he could trigger an evolution in Melissa's Quirk the same way he had with Yu, he needed direct contact with the areas of highest nerve sensitivity.
And on Melissa's body, those areas were obvious.
Izuku took a deep breath. This was for science. For research. For the advancement of Quirk knowledge. It was not a perverted request. It was an experimental hypothesis that needed to be tested. He told himself that at least three times before speaking.
"Melissa," Izuku said, keeping his voice as professional as possible, "I need to ask you a question. It is scientifically relevant, I promise."
"Alright," Melissa replied, though her voice came out a bit higher than normal.
Izuku took one step closer. Then another. Until he was less than a meter away. "Based on the data we have collected," Izuku began, "and the theory that my Quirk optimizes complete biological systems through contact with areas of high nerve sensitivity... I need to test if my hypothesis is correct."
"What hypothesis?" Melissa asked, slightly tilting her head.
Izuku raised his right hand slowly. He held it in the air between them, trembling slightly. His eyes met Melissa's, looking for any sign of discomfort.
"Melissa," Izuku said, feeling all his scientific training abandon him and letting himself be led purely by instinct and a hunch he could not rationally explain, "will you let me touch your breasts?"
*****
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