Sero wasn't sure what to expect when it came to Izuku's training, but running through the city in the dead of night wasn't it.

The strength quirk he had was amazing to watch at night, the way it would light up around Izuku, crackling as he flexed and worked his body. The way he could throw himself from building to building without breaking a sweat was awe inspiring. Especially since Sero was nearly dying trying to keep up with him.

Once Izuku finally came to a stop, looking out over the night lights of the city, Sero collapsed into a panting pile next to him. "Why- why are we doing this?"

Izuku spared him a single look. "The way you can barely stand right now should make the purpose blatantly obvious. You need to work on your stamina, along with your agility and stealth. This works all of that, along with quirk control."

Sero nodded in understanding as he looked up at the night sky.

"Plus," Izuku added with a faint smile he knew Sero wouldn't see in the darkness. "It's fun."

The ragged teen on the ground let out a barking laugh. "You, my dear friend, have a very different definition of fun."

Izuku blinked. What had Sero just said?

"What did you just call me?" he asked, no malice in his voice. The only emotion Sero could find was... astonished.

"My friend. Wouldn't you say that's what we are now? After all, you saved my ass at the complex, and I plan to save yours." Sero was slightly worried he'd messed up. What if Izuku didn't think of it the same way? What if he was utterly offended Sero would dare to consider them as anything other than acquaintances?

Izuku tilted his head, his freckled face of contemplation lit up solely by the city lights. Then he nodded. "Friends it is then."

Sero let out a breath of relief, watching as Izuku, for the first time, seemed to struggle to find the right words to say. He opened and closed his mouth a few times, like he couldn't decide how to start.

"What is it?" Sero asked, sitting up. It had to be serious if it was tripping up Izuku. He'd never seen the other boy ruffled like this.

"What... what exactly does being friends entail?" Izuku finally asked, seeming to refuse to make eye contact.

Sero stared at him a little confused. "Izuku... have you never had a friend before?"
The question was supposed to be innocent, just trying to test the waters, but Izuku took it harsher than Sero had intended.

He shot the black haired boy a sharp glare. "Sorry being a villain's kid who went to public school registered as quirkless didn't leave many options for making friends," he hissed, all the anger and hurt he'd bottled up over the years in that hellscape escaping in those quick words.

Sero flinched, like the words had landed a physical blow. "I'm sorry, I didn't mean-"

Izuku didn't let him finish his apology. He abruptly stood up and walked to the edge of the rooftop. "C'mon, you've had a long enough break."

"Izuku, can we just-"

"Do you want me to train you or not?" Izuku snapped at him, his eyes narrowed to slits. The glare was almost painful.
Sero grimaced and nodded, walking over to the boy. And just like that, they restarted their journey through the city.

They quickly fell into a routine through the next week and a half. The evenings would consist of stretching, a light warm up, a few muscle building exercises that Izuku would rotate out throughout the week, and then they would run through the city.

They hadn't done much talking since Izuku had snapped at him on that roof top and Sero was desperate to fix the rift he'd torn between them. He had finally been getting somewhere with the villain boy, now he was back to square one. Actually, he was further back than that.

They were on their nightly run through the city, jumping across roofs and dodging obstacles as they came across them. It was done without words, Izuku only sparing Sero a glance every once in a while to make sure the boy was still there.

Sero's skin was starting to crawl from the lack of interaction. He was a social person, being this close to someone so often and saying nothing was killing him. Being this close to Izuku and saying nothing, barely being acknowledged, was killing him.

So Sero's incredible and analytical mind came up with the perfect plan. Absolutely air tight. Nothing could go wrong.

Sero managed to make it right up close to Izuku, and tapped his shoulder. The other boy looked over at him in confusion, wondering if something was wrong. Sero had stopped a few feet behind him, looking at him with a smile to rival the cheshire cat.

"Tag, you're it."

Izuku cocked his head to the side. Of course he knew what tag was, but he... he had never actually played before. Even as a kid, he had limited contact with others. The only person his own age he was allowed around was Katsuki, and tag wasn't high on their list of games.

"Come catch me if you can, Izuku," Sero cooed at him, instantly shooting his tape off to the right and swinging to the next building.

Izuku watched him run for a few moments. He was stunned. Sero wanted to... play tag with him? Is that what friends did? Played childish games to spice up a mundane routine? Whatever Sero's reasoning, Izuku was eager to play along. He just wanted to play, really. He hadn't since.... probably since he got his quirk. All he's done since then is train and study. Had it really been that long?

Izuku huffed at the thought before he decided to not let it ruin his quickly brought on good mood. He took off after Sero, skillfully leaping across the buildings.

Sero really never stood a chance, and he knew that. The game was just an ice breaker anyway. A way to get Izuku to finally acknowledge him again.

And seeing as Izuku had tackled him to the ground, a small and startled laugh escaping his lips, Sero thought it did a damn good job. He couldn't help the stupid smile on his face as he looked up at the boy who looked genuinely happy for the first time.

"This means you're it, right? Because I- I tagged you," Izuku asked, leaning down slightly, excitement dancing in his eyes. He cared about nothing else other than this game of tag Sero had started.

The boy under him nodded his head, "Which means you need to get off of me and run."

Izuku's eyes widened in understanding and in a single second he was gone. Sero could do nothing more than blink for a second as he tried to comprehend how quickly he disappeared. He shook himself back to reality when he realized that Izuku was just getting further away and harder to catch. He was quick to his feet, chasing after the green glowing streaking across the night sky.

The two boys spent hours playing the silly game, extending their training much longer than usual. Neither seemed to care as they chased the other down, hiding behind vent shafts and dumpsters as the city turned into their playground. Izuku wasn't sure he'd ever laughed so much or felt so carefree. Sero was just relieved the boy was talking to him again.

Eventually Sero could barely stand anymore. He wasn't nearly as well trained as Izuku and was wearing out much faster than the other boy. "Hey, I think we should probably call it a night," he panted as he finally caught up with the green lightning.

Izuku looked back at him, clearly confused as to why they were cutting the game short, but he took in the sight of Sero. The boy was ran ragged, panting and drenched in sweat. He looked like he'd fall over any second. Izuku turned his gaze away, looking at the horizon where the sky was just barely starting to brighten. They had been messing around all night.

"You're probably right, it's morning now." Izuku tried very hard to keep his disappointment to himself, but Sero had gotten quite good at reading him the past few weeks.

The raven haired boy shot him a teasing smile, bumping their shoulders together. "Don't worry, lightning bug, we'll play tag again tomorrow." He paused and thought something over. "Or today? Tonight? I don't know."

But Izuku had stopped listening.

"Lightning bug?" Those two words were playing on a loop in Izuku's head now. It was... a nickname. One without any sort of malice. It was almost... endearing? What the fuck.

With an out of breath cackle, Sero said, "Because of the quirk that makes all the green lightning surround you. In the dark, you almost look like a giant lightning bug."

Izuku cocked his head as he looked over Sero. "Is that... a bad thing?"

Instantly the black haired boy was shaking his head. "No, no, not at all. It's actually really cool to see, lightning bugs are like, the coolest bugs."

Izuku looked at him with faint amusement as he fumbled to explain his thought process behind the nickname. "I guess I won't kill you for the nickname then, since it's so cool and all."

Sero looked him up and down. "If I didn't know better, lightning bug, I'd think you were trying to make a joke."

Izuku bumped his arm as he walked past, right over to the side of the roof they were stopped on. "Trying? I'm pretty sure I succeeded."

"Oh, look at you, bantering. I didn't know you had it in you," Sero teased, crossing his arms over his chest.

Izuku just rolled his eyes, but Sero could see the smile he was trying so hard to hide. "See you tomorrow, tape boy."

He was already leaping away as Sero shouted, "Awe, you gave me a nickname!"

this was fucking adorable and i won't take criticism. also lightning bug is an under appreciated nickname for izuku and i plan to change that.