**Accidental Discovery**

Katsuki Bakugo glared at Izuku Midoriya, his arch-nemesis since childhood, as they stood facing each other in the U.A. High School courtyard. Their rivalry had been a long-standing one, with Katsuki always trying to one-up Izuku and prove his superiority. But today, Katsuki was feeling particularly annoyed. Izuku had managed to pull off an impressive rescue mission during their training exercise, and Katsuki was determined to get under his skin. "Hey, Deku, think you're so smart with your little heroics, huh?" Katsuki sneered, his eyes narrowing. Izuku, oblivious to Katsuki's teasing tone, beamed with pride. "Hey, someone's got to keep up with you, Kacchan!" Izuku replied, using the affectionate nickname that Katsuki had long since outgrown. Katsuki's scowl deepened. "Shut up, Deku. You're not even in my league." But Izuku just chuckled and started to walk away, and Katsuki's anger got the better of him. He reached out and ruffled Izuku's hair, a gesture that was meant to be annoying but somehow felt...intimate. "Good boy," Katsuki muttered, the words tumbling out before he could stop them. He didn't think much of it, just another phrase he'd picked up from his mom. But as soon as the words left his lips, Izuku's expression changed. His eyes sparkled, and a flush rose to his cheeks. He looked...different. Katsuki couldn't quite put his finger on it, but Izuku seemed to...relax, somehow. His shoulders dropped, and his entire demeanor softened. Katsuki raised an eyebrow, intrigued despite himself. "What's wrong with you, Deku?" he asked, his tone a little softer than usual. Izuku blinked, looking around as if he'd just woken up from a dream. "N-nothing, Kacchan," he stuttered, his eyes darting back to Katsuki's face. Katsuki's curiosity got the better of him. He reached out and poked Izuku's shoulder, just to see if he could trigger the same reaction again. "Good boy," he said, his voice low and teasing. Izuku's eyes locked onto Katsuki's, and that sparkle was back, stronger than before. He took a step closer, his face tilted upwards, and Katsuki felt his heart stumble. What was going on with Deku? Over the next few days, Katsuki found himself testing Izuku's reaction to those two simple words. It started as a game, a way to get under Izuku's skin and watch him squirm. But as the days went by, Katsuki began to realize that Izuku's response went far beyond mere annoyance or frustration. Izuku would light up, his eyes shining with a soft, almost...hopeful expression. And Katsuki couldn't help but enjoy it. Their rivalry slowly began to shift, with Katsuki's teasing taking on a new, flirtatious tone. He'd brush against Izuku's arm, or lean in close to whisper "good boy" in his ear. Izuku would blush, but he wouldn't pull away. Instead, he'd seem to...lean in, just a little. Katsuki's touches grew bolder, his fingers grazing Izuku's skin as they worked together on training exercises. Izuku wouldn't protest, just look up at Katsuki with those shining eyes, and Katsuki would feel his heart stumble. One day, as they were walking back to their dorm, Katsuki leaned in close and whispered "good boy" in Izuku's ear. Izuku's face went beet red, but he didn't pull away. Instead, he looked up at Katsuki with a secretive smile, and Katsuki wondered if Izuku was actually...hoping for something more. Was Izuku waiting for him to say those words again? To do something more? Katsuki's heart skipped a beat as he met Izuku's gaze, and for a moment, they just stared at each other, the tension between them palpable. And then, without thinking, Katsuki leaned in, his lips brushing against Izuku's ear. "Good boy," he whispered, his voice barely audible. Izuku's eyes fluttered closed, and Katsuki felt his heart soar. What was happening between them? And where would it lead?