AN: We had one big review yesterday, so I'm gonna respond to it here!
Twinklestabber: Thank you for the feedback and advice! When it comes to the tagging... I honestly just hadn't really known what to tag it with so I just picked the two I remembered seeing often. I've since changed it to Adventure General, but I'm still not sure if that fits well, so if anyone thinks another tagging option would work better, please let me know! As for Izuku's power, I had kinda figured if Izuku was given a power with any sort of open-ended-ness as to how it worked, he'd absolutely run with it and make it as busted as he could, like I've had him do here, and with All Might's quirk... I honestly just felt like there was so many reasons not to take it, but even just his biology, since he wouldn't be able to just pass it on again, Izuku felt that being the end of the legacy All Might was a part of would be problematic.
Katsuki smirked as he blasted himself towards Deku. His opponent was smart, not that he'd ever admit that, but really? Using Katsuki's home element against him? Katsuki already knew the exact time he'd have to dodge the next attack, because he'd taken years figuring out by muscle memory exactly how his own explosions worked.
Katsuki braced to throw himself to the left, towards the side of Deku that didn't still hold the mysteries of what his new arm could do, and was knocked off his feet by the explosion projected from his opponent's hand.
"CL-20, Kacchan! More efficient, and more importantly, with a higher detonation velocity than nitroglycerin!" Well damn, his own muscle memory would be working against him then. Katsuki caught himself in midair with his explosions burning retrograde, and turned towards Izuku to see that swarm of crystals from his back heading towards him through the dust of the previous explosion.
He let out a large blast, which knocked away most of the shards, many of them shattering against the ground, but a few managed to make their way through and give him quite a few small cuts. Before he could do anything else, though, a black cable swung out from the dust cloud below and yanked him back towards solid ground, directly into a pool of what felt like acid.
Katsuki scrambled out of the liquid, looking up to find Deku there, his sword sheathed and his left pointer finger formed of a crimson crystal, dripping liquid metal. His opponent slammed his right fist against his chest, his jade arm ringing, and launched himself towards Katsuki, who sprang into action in turn.
Katsuki slid slightly to the right, dodging past the arm he knew would easily knock him out of the arena on contact, and felt Deku grab his right shoulder, and his pointer finger started burning through Katsuki's sleeve. At the same time, Katsuki's hand found its own grip upon Deku's right shoulder, and with a grip and an explosion, the jade arm fell to the ground, causing Deku to stumble a step back.
Katsuki smirked, as the battle was turning in his favor, until he was suddenly knocked from his battle fervor, looking at Deku missing his right arm, just like he once had. Once again, it was Katsuki's fault, and he could practically see the younger Deku there, scrabbling through the river to try to find any of his arm that was left. Katsuki was broken out of this memory as Deku pushed him down with his remaining arm, and he saw the boy's eyes cross for a moment before he started feeling a heat on either side of his neck.
Izuku kept pouring his light forward, his crossed eyes projecting twin lasers on either side of Kacchan's throat, one of the only ways he could think of that could successfully hold someone who could blow up anyone and anything nearby.
"Bakugou, can you move?" Midnight called out, to which Kacchan reluctantly admitted that he could not, at least not without beheading himself. "Then the winner of the Sports Festival, by the most unconventional pin I've ever seen, is IZUKU MIDORIYA!" The crowd erupted into a frenzy as Izuku shut his lasers off and offered Kacchan a hand up.
"I don't need your damn help..." Kacchan grumbled, but eventually took the proffered hand and stood up, after which Izuku raised both their hands towards the sky, causing the stands to get even louder in their excitement. At that moment Izuku realized that he was still down an arm and quickly pulled it back towards himself, the crystals reattaching where they ought to.
Smiling and waving, Izuku walked out of the arena with Kacchan, who, despite being obviously upset at his loss, still seemed pleased to have been pushed as hard as he had.
After dropping off Kacchan to be treated for his minor acid burns due to his caustic mercury attack, Izuku returned to his class' stands to find his whole class waiting for him. He had to activate Black Diamond form just to keep from shattering across the ground when his clear buddy Hagakure tackled him with a hug, which was met with some laughs by the group, although he did notice Momo seemed a little upset. She cheered up though, when he called her over and said he wanted to talk to her in private.
In one of the more secluded hallways, the two of them stood, Izuku trying to figure out how to say what he wanted to say to her.
"What was it you needed, Izuku?" Momo asked him, slightly turned away from him, but obviously still looking straight at him with one eye.
Izuku reached behind himself and unfastened Kuromu's sheathe from his belt, before reaching forward to hand it to her.
"I-I feel like you should have this." Momo stood there, clearly acting like this was not what she expected this meeting to be about, before she regained her composure.
"W-why do you think I should have this again?"
"Because you and I have both seen how this sword can assimilate other materials, but it only does that when you're the one wielding it, not when I have it. I just felt that it'd be in better hands if you took it." Momo seemed to hesitate for a bit, but eventually took the sword by the center of the sheathe.
As Momo grasped Kuromu's sheathe, she felt something tingle in the back of her head, like she could tell somehow that the sword was accepting her as its new wielder. She vaguely remembered that Izuku had said at some point that he could sense intentions from the sentient blade from time to time, and shook her head as she chalked it up to that.
"You should probably go back to the field for the award ceremony, Izuku, they're about to begin." Izuku realized she was right and thanked her for the heads-up, running out of the hall to go join the other boys who had placed in the top four of the tournament.
Momo felt her heart clutch for a moment, but she knew it was probably better this way, and resolved to keep standing by Izuku's side for as long as she could.
The ceremony was short, with All Might handing Iida and Todoroki each their third place medals, along with a hug and some advice to become better heroes, while he gave the same to Bakugou and Izuku, although they had achieved second and first place respectively.
Momo was slightly upset that she couldn't have placed higher, but she also knew that if she had beaten Midoriya she would have been against Todoroki anyways, and she had no idea how she could easily beat his brute force, so she resolved herself to be happy with the placement she got. After the award ceremony, she head home, Kuromu in tow, ready for the long break they all deserved after their fighting that day.
Told you that I had decided to re-include one of the earlier suggestions, although I don't know for sure if black-white-rose is still reading!