3rd person POV:

'Great. The one fight where I'm willing to use OFA and I can't legally.' Izuku pulled Kandaina and Chujitsuna out out preparing to fight. "Stay out of this boy, my business is with these fake heroes." "You see that's where I can't let that happen. If you're going to hurt someone, then I'm getting involved." Izuku stood in front of Iida prepared to take Stain on. "You've got a 55 million Berry bounty on your head Hero Killer Stain. I'd rather not fight you, but I will if I have to." Izuku was not unwavering to make the Hero Killer smirk. "Nicely done hero, but let's see if you can back that talk up." Stain pulled his katana out to face Izuku. "I'm no hero. I'm a swordsman." Both charged at one another with Stain giving the first strike. Izuku blocked this with Chujitsuna before the Hero Killer pulled out a knife to attack with. This was where Kandaina had come in handy to block. Noticing that Izuku wasn't just any swordsman, Stain began to pick up his game by constantly slashing at Izuku as he continued to block. The echo of steel rang in the dark alley for both the pro Native and Iida to watch in amazement.

"Just who is this guy anyway?" "Green Demon of Mustafar and the greatest swordsman in Japan. Izuku Midoriya." Iida began to cry realizing he made a horrible mistake and couldn't do a thing about it. Because of his selfish act, Izuku had to fight and protect him against Stain on his own. The two watched as Izuku pulled back to gain some ground before having a knife thrown in his side. "DAMMIT!" Izuku glanced down to see it was in a spot that would cause issues if he left it in, so he took a moment to pull it out and throw the knife to the side. In this time, Stain came at Izuku's side for some reason. "Midoriya! Don't let him get your blood!" Iida shouted this for the young swordsman to prepare an attack. "Cross Slice!" This pushed Stain back a bit for him to remain where he was. "I must admit boy, you're quite skilled. But why protect the fakes? I only wish to take them and not you. It would be a waste to kill such a worthy hero like yourself, so why do you?" "When someone has conviction, they'll fight for it until the bitter end. Right now, this is just one part of my conviction with you being a stepping stone in my eternal uphill battle. Don't get me wrong Stain. You're a formidable foe, but I won't fall to you. Not you, not anyone again."

This comment made the Hero Killer smile. "Quite the determined one, but no matter." Stain came at Izuku again with several blades being sent at him. Izuku blocked them before having Stain's sword come for a downward strike. This was deflected with the blade being thrown into the air before the Hero Killer pulled another large knife out to nearly slice Izuku. 'Gotta get some distance. This guy has too many weapons that I can't see off the bat.' Iuzku looked for the best moment to gain an opening, but was unable to find one through normal means. Attack after attack, Izuku was becoming overwhelmed and needed to think things through a bit more. 'Come on Izuku, Think!' It was at this moment that the young swordsman activated Observation Haki to see an extremely small opening he could use between Stain's attacks. He was able to strike during it to take advantage of and slice some holsters for knives off the villain. Izuku noticed the knives holster to see it had almost two dozen on it alone with no holsters empty. "What are you, knives weekly!?"

Izuku calmed himself before remembering what Zoro said a little while back about Armament Haki. 'The key to Armament is to think it as just a form of armored layer over your body.' Izuku held his swords down while focusing and clearing his mind. "What is this? Are you giving up?" 'Imagine a barrier over my swords.' Slowly but surely, a dark substance was covering Izuku's blades to surprise everyone. "Is that a quirk?" "No. It's something completely different." The sound of a woman was heard to show Itsuka, Momo, and Robin walk into the alley. "It would appear your friend has found a way to control Armament Haki." Itsuka and Momo watched as Izuku finished the coating of his swords to charge at the Hero Killer. In defense, Stain came at him with knives for them to get cut in half. "What!?" 'Keep the image in your head. Don't let your mind falter on you.' Izuku kept his mind concentrated on what he was doing with little margin for any other conversations in his mind.

https://youtu.be/9OwLhsCL0x8

Izuku came at Stain with his Haki covered blades to force the Hero Killer to remain on the defense. 'What is this boy doing? What did he do differently?' Stain began to attack Izuku the best he could to only find himself breaking his blades on Izuku's. "Black Blade arts." Izuku held his blades in an iconic position of his for Momo and Itsuka to smirk knowing this is all over when the attack connects. "Strike of Earth's Ascension!" Izuku charged at Stain with believing he would win when it connected. Unfortunately, he lost his focus for the Armament Haki to be taken off his blades. The Hero Killer noticed this to block the attack with some of his final blades. When the sound of steel connecting came to the young swordsman's ears, he knew he screwed up somewhere in that time gap. "A rather interesting trick, but it would appear that you aren't in full control of it yet." Stain was able to push Izuku back and attack him. He was able to defend against it, but the young swordsman was becoming more fatigued. 'Why am I so tired right now? Is it a drawback to not being fully in sync with Armament Haki yet?'

"Now die!" Stain came at Izuku prepared to take him down with Itsuka about to jump in. Before she did however, Robin stopped her to shout something. "As of right now Izuku Midoriya I the archaeologist Hero Devil's Child give you authorization to use your quirk!" Izuku heard this with Stain barreling at him. His attack was stopped by chujitsune. Both were at a stalemate with Izuku glaring at the Hero Killer. "If I take you down, it'll help my friend who has stumbled off the path he rightfully needs to remain on." 'OFA, Full Cowling 8%!' Izuku shoved Stain off him to charge back at the Hero Killer. His first attack was dodged, but the young swordsman rebounded and attacked again from using the wall behind him as a jumping platform. Izuku was able to cut Stain's arm a bit before using the other wall of the alley in a similar act as the first. Attack after attack, Izuku came at Stain with him gaining more and more speed. Eventually, the Hero Killer had the rhythm down to attack Izuku. This was met with the young swordsman changing his trajectory slightly to hit the ground below Stain and knee his jaw jumping up. Once this happened, Izuku jumped up towards the rooftops before changing his angle to face Stain.

"Now Hero Killer, it's time I finish your rain of terror once and for all." Izuku pushes himself off the wall to come at Stain with an immense level of speed. He twirled his body before initiating his final attack. STRIKE OF THE VENGEFUL TIGER!" Izuku was able to connect with Stain who tried to protect himself with his blades, but this did little as the Hero Killer was shoved into a wall. The act created a hole in it with Stain unconscious inside with blood coming out his head. Izuku was panting in pain as he stood tall. He walked to the Hero Killer to bow to him. "Thank you *pant* for the fight." Izuku placed his blades away before going towards Iida. "Can you stand?" Iida was crying on the ground in his own self hatred. "Why? *hic* Why help me? This was my fault, so why!?" Izuku held an emotionless face before clenching his fist. "IT'S BECAUSE WE'RE FRIENDS DIPSHIT!" Izuku hit the engine quirk user in his head to create a notable bump on the top. "When you have a problem, you talk to someone! Don't think something stupid like going after someone like the Hero Killer is smart! You're better than that!"

Iida remained silent realizing Izuku actually was worried for him. "You could've died, so please use better judgement next time. Your brother would never forgive himself if you went and died because of him. How do you think he'd feel? Ingenium may not be able to be a hero anymore, but you can continue his legacy. Be the hero your brother was and continue to honor what he stood for. What happened was a tragedy, but the good he did will not perish with him. The inspiration he gave to people like you is why we strive to do what is right." Iida started to cry a bit before nodding. "Thank you Midoriya. You're a good friend." Izuku gave Iida a hand up with him slowly beginning to move again. Meanwhile, Robin helped Native up with Momo and a Itsuka disarming Stain and wrapping him up. Luckily the garbage dumpster nearby had some kind of rope in it for them to tie the villain up in. When everyone was up, they began walking out of the alley to the open streets. The nightmare of the Hero Killer fight was over.

Izuku POV:

After heading to the open streets, we were met by most of the Straw Hats and some pro heroes. "Robin, is everything ok?" "Why yes navigator. It also appears our young student found a way to use Armament Haki. At least, to some degree." Chopper came over looking around before asking me a question. "Where'd Zoro go? He was with you." "I honestly don't know. I was running straight, next thing I know is he's gone." On cue, Zoro came running here panting for air. "Nice job disappearing on me kid!" "I didn't disappear on you! You disappeared on me!" "Yeah right!" "Zoro you suck at directions. I doubt you were going the right way to begin with." "Shut up Usopp!" We started laughing a bit before Chopper found something that scared him. "IS THAT THE HERO KILLER!?" He shouted this for everyone to look behind us to see the villain in ropes. "Yeah. That's him." Everyone held their mouths opened completely baffled he was taken down.

"Everyone! Look out!" Luffy, Jinbeii, and Franky came running towards us for the one Nomu with wings to come after me and take me into the sky. "Izuku!" It began taking me high into the air with Luffy stretching his arms. "Hang on. Gum Gum-" Before he could though, Stain took a knife we overlooked to cut the restraints off and lick the blood that was from the creature off Nami's cheek to paralyze it. 'So that's what his quirk does.' Stain jumped up to stab the thing in the head, killing it in the process. 'The Hero Killer saved me?' Stain grabbed me before landing on the ground. "You fake heroes are nothing. You all must be purged." The sash over his face fell to show a man of ironclad convictions ready to face the world.

"None of you are worthy to kill me. There is only one man in this world worthy of that title." Stain looked up to the heavens before shouting at the depths of his lungs. "ALL MIGHT IS WORTHY!" In fear, I jumped up and pulled my swords out preparing for another fight. 'This isn't gonna end well.' I waited for his next move for him to remain perfectly still.

"Is...is he dead?" Usopp was hiding behind Sanji as I glanced at his face. "He's unconscious." Chopper came running towards us to check the Hero Killer's vitals. "I think a broke rib punctured a lung! He needs a hospital right now!" Nami called a hospital with Franky and Jinbeii helping support Stain where he wouldn't die of blood pooling in his lung while Chopper did what he could on the spot. "Are you alright?" Brook came over to notice the cut on my side. "It's nothing. He needs the immediate help right now." I walked to the side to relax a bit from the nightmare that just unfolded. 'It's over. This night is finally over.' I felt myself fall out of consciousness with the stinging on my side being unbearable.

Two days later

After the capture of Stain, Native, Iida, and myself were brought to a hospital to get patched up. From what I was told, Stain's cut was worse than I believed hitting a vital. I probably didn't feel it since I was so hocked up on adrenaline. It was able to be patched up, but I knew was that I was gonna have another nasty scar on me. "Izuku, how are you feeling?" Zoro and the rest of the Straw Hats came into the room with some other people to greet me and Iida. "Manual sir, what's going on?" "I think I can answer that young man." A man with a dog head came in front to speak. "Hello, my name is Kenji Tsuragamae. Chief of Hosu police." Both me and Iida got up to bow. "First and foremost, I'd like to thank you Izuku Midoriya for what you have done. Thanks to you, the Hero Killer will no longer be an issue." "I just did what I could sir." "Indeed. And thanks to you being given authorization and having a bounty hunter license, you handled everything legally. However, Tenya Iida." Iida stiffened when hearing his name. "You had neither when fighting the Hero Killer. In all technicality, you should be arrested for what you've done."

"What!? But the Hero Killer did the exact same thing he was doing this entire time! Does that mean nothing!?" Luffy was mad with the chief explaining. "Justice needs to place boundaries somewhere. We can't pick and choose who we let break the rules and who gets the whip. Technically Iida had broken the law as well. He used a quirk not in defense and willingly went after someone without any authorization." "But that isn't fair-" "Luffy! He's not wrong." Sanji spoke up for the room to become silent. "Now if the story would play out exactly as it would, Iida would be arrested. But he was also a victim in this and I'm not exactly fond of arresting those who aren't truly the villains in stories like these. So here's what will happen. Iida had been told to go assist Native where he was attacked by the Hero Killer. There, Midoriya had discovered them with the tale being about the same as what happened. Since he did everything by the book, nothing has to be changed. The only people who know of the variance are the people in this room and a few others. The final result is still the same, but the beginning had been changed. Any objections?" We remained silent as a way to say we're all in agreement.

"Midoriya, I also need you to sign this." Tsuragamae gave me a clipboard with the standard papers for when I'd take down pirates or villains with bounties on their head. I filed them accordingly before giving the clipboard back. "Stain had a 55 million berry bounty on his head. In yen, that's 5.5 million." The chief passed me a check that I put to the side. "Now that that matters settled, I'll leave you all to your business." Chief Tsuragamae left for the Straw Hats to hold a grim look. "I'm sorry if I caused any problems for you all." They glanced at me not knowing what I meant. "Sorry, but we're not mad at you. It's something else." I didn't know what they meant for Nami to point out what it is. "A pirate group came out of the Grand Line called the Arlong pirates. They're not the nicest people with our crew having a bad memory with them. Me personally." "So they're a group you're going after?" "Sorta, but there's more to the story." Sanji said this to confuse me a bit. "When Arlong and his crew came here, the first thing they did was steal a ship from a pro hero called Selkie and took a sidekick of his and a student from UA that was doing a work study with him." When I heard that a UA student was taken, I remembered the name Selkie right off the bat. 'Tsu.'

And that finishes this chapter. So the next will be a bit of a backstory for what happened to Tsu to be captured by Arlong and his pirate crew. See what'll happen next time when Izuku and everyone finds out about this. Hope you all enjoyed and thanks for reading.