Izuku POV:

As the setup for the invasion went underway, me, Momo, Itsuka, and the rest of the crew of the Strawhats began to sail out to the destination of where the stolen ship was last spotted. On the way, we were met by a marine vessel and another ship pulled by what looked like sea snakes. "Hey Izuku! You ready!?" I glanced over to the ship with the sea snakes to see Hancock and Ochako on it. "Oh I'm itching to cut me up some bastard pirates." I started to pull out my blades a bit before I heard Kaachan scoff. "By the time I'm on the ship, there won't be any fishmen for you to fight Deku." We both smirked before Luffy ran over to look at Kaachan for a minute. "WOA! YOU LOOK SOO COOOL!" "Is this really the time to be doing this?" Momo stated this as we began to head near a bunch of other ships. I couldn't believe how many of a turn out this was. I could see ships belonging to the Heart Pirates, the Firetank Pirates, some pro heroes, and....mom on Hawkeye's ship?

"Hi sweetie." "MOM!? WHAT ARE YOU DOING HERE!? IT'S DANGEROUS!" She smiled and laughed a bit at this for it to only surprise everyone. "It's alright Izuku. I can manage myself." "And if she cannot, I shall be there as support." Hawkeye stated this with Mr. Aizawa and a woman with pink hair and some kind of umbrella walking over. "So this is your son Hawkeye. Didn't expect him to look so scruffy."

"WHAT WAS THAT YOU SAID ABOUT IZUKU!?"The girls began to argue with the unknown woman as Zoro came over. "Perona. Did you get what I asked?" "Could you at least talk to me a little better instead of saying hey!...And I did." The girl now known as Perona threw something wrapped up over to Zoro for him to unwrap it and show it was a sword. "The legendary demon blade Muramassa. Said to be cursed and will kill its owner if they deem them unworthy to wield it. Don't know what you plan to do with that, but go right ahead and cut your head off for all I care." Zoro smiled at this before tossing the blade at me. "Izuku. Think fast." I grabbed it to pull the blade out from its sheath to marvel at the craftsmanship.

"That sword was forged by legend from the blood of a demon that was killed near the minerals used to create that sword. They say that it's because the demon's soul is trapped within the blade that many who hold the sword die by its end. From what I was also told, the blade can ignite blood like a flint to lighter fluid." "Wait, so you gave him a cursed blade!?" "And? I have 2 of them." Usopp and Nami hit Zoro over the head in anger. "HE ISN'T YOU THOUGH!" 'Well, I came into this hoping to fight with everything I had, so it would be a waste to not use it.' I pulled the blade out of it's sheath completely and held my arm out. "Izuku. What are you doing?" Itsuka asked as I smiled. "I wonder what's stronger? The blade's curse, or my luck." I threw the sword up in the air with it rotating for everyone's heart to stop. Ochako, Momo, and Itsuka looked at me in fear as it came down. It looked like the blade was going to slice my arm off before it moved to have the end just miss my arm and impale the deck of the ship under my arm.

(Imagine Izuku as Zoro)

"Thank you for the gift Zoro. It won't go to waste." "Nicely done kid. Couldn't have done it better myself." "Wait a second, didn't you do that with your cursed sword?" Tashigi asks, turning to the moss head. "Yep, great swordsmen think alike." "To be fair, I did that too with my first cursed weapon as well." Hawkeye adds in. "I'm surrounded by idiots." Nami groans pinching the bridge of her nose.

"Alright. We're facing fishmen, so we'll need to be extra careful. Surgeon! We need you to make a zone around the ship and prevent any fishmen from escaping. Firetank pirates, keep a perimeter around the zone in case the enemy does try to escape. Meanwhile, a small group of the Strawhat pirates, Kuja Pirates, and the fleet under Vice Admiral Smoker will infiltrate the area to retrieve the hostages. When that is done, we have orders to fire on the ship and sink it along with the pirates aboard." A member of the police stated this for two of the three groups to begin their role. "I've always wanted to go fishing." I state with a smirk causing others to groan at the pun. "You're not going with that group." Nami points this out for everyone to look at her. "If anyone understands Arlong as well as his crew, it's me. Don't think you can win against him and don't think that I'll allow you to go anywhere near him. I don't care if you think poorly of me, but I'm the voice of reason here and if you go and get hurt, we pay for your expenses and we lose our money." "Should've figured that was her logic." The guys said this before getting a hit on the head. "Let him go. I'm sending Tashigi and Bakugou, so why not Demon, Creati, and Battle fist?" Smoker butted in along with Hancock joining in. "I am certain that Uravity can handle this as well. So do not think poorly of them."

"Since when would you all have to pay for us getting hurt? You have Chopper and he's a doctor, plus this week alone I've seen Sanji lose more blood than humanly possibly on several occasions." Nami thought of this before groaning and accepting. "FINE BUT DON'T BLAME ME WHEN WE'RE BACK IN DEBT!" 'Is money all this woman thinks about?' I start heading to the rowboats with Itsuka and Momo before uniting with Kaachan, Tashigi, and Ochako. "It's nice to see you again Green Demon. I heard you've gotten stronger since last time." "I have. And I'm ready to take on the son of a bitch who wanted to hurt my friend." We began rowing to the ship with the members of the fishman pirates attempting to shoot at the barrier they were in. This failed on their end with the cannonballs bouncing off the wall and into the water. "So where are we entering on the ship?" "The Stern. There's a blind spot and I noticed there weren't any fishmen in the area." Me and Kaachan nodded at Tashigi's input before rowing to the back of the ship. There, Momo made a grappling hook for us to sneak aboard. To try and avoid any major issues, Tashigi stayed at the bottom of the boat to keep the number of people on the ship at five. Not as many to slow us down, but not too little where a fight would be an issue.

As we came to the entrance to below deck, two fishmen walked out having some kind of argument. "Arlong, this is too far! I did everything you asked, so let the two girls and my friends go!" One was without a doubt Arlong, while the other looked like the octopus Hatchan. "How many times have I told you Hachi!? When the Arlong Empire is free to bloom in this world, we'll part ways!" "That wasn't the original deal though! You promised Camie and Pappag would be free if I got you out of our world and into this one!" "Was that it? I don't remember it so well. AHAHAHA!" "Euuu." The octopus seemed enraged with the fact the two weren't on good terms maybe coming to our advantage later. We kept heading downward to see some of the fishmen still lingering to sneak past them. Once we got to the prison cells for villains, we noticed Tsu, Selkie, and two others that looked like a mermaid and a starfish. "Tsu." Getting her attention, Tsu looked up to see us. "What are you all doing here?" "We came to rescue you." Her face went dark at the comment Ochako made before saying something. "It's pointless. No matter what, we're doomed here." I couldn't imagine what Tsu had to go through in order to say there's nothing worth trying to escape. "We'll get you out in a minute. Just wait." Momo made a lock pick for the cell before opening it. When she did, we walked into the cell to try and help her up. When we did, I noticed something on Tsu's arm. "Tsu? What's that?"

She started to cry before explaining. "As I said, it's pointless to free us. We're doomed to never escape Arlong." Every fiber of my being was telling me to hack Arlong to bits for what he did. I wanted to make him suffer for hurting a friend of mine before taking a deep breath. "C'mon. Grab the other two. From what the octopus said, they're being held here against their will." Kaachan grabbed the starfish and Itsuka grabbed the mermaid before we began to leave. Once we got above deck however, we were met with the army of fishmen as well as Arlong standing in front of us. "You thought you were very clever little human. But little did you know, we've known you were on this ship and we were waiting for the best moment to rise your hopes up and destroy them." He started laughing before Hatchan came over "Camie! Are you ok!?" A stingray guy that looked like Kuroobi grabbed the back of his shirt before pulling Hatchan back. "Get your act together and get ready for a fight! If you don't, I don't think we can guarantee that your little girlfriend will be fine." His fists shook before standing up. "Forgive me." The octopus whispered this for some reason before grabbing his swords. "So what now Arlong? You're cornered. You have an army of ships out there with the chances of you escaping being next to impossible. Whether you like it or not, you're going down today for good." He smiled at me before speaking. "Maybe, but I'll have my fun KILLING YOU HUMANS FIRST!" He charged at me to send me into the distance and hit the ledge. "Prepare yourself human, for you are about to see the all mighty power of what a fishman can really do!" I groaned before speaking. "Great. Now I can get to try out my new sword." I smiled while pulling out my blades.

3rd person POV:

As Izuku's fight with Arlong began, the other members of the Arlong pirates began charging at everyone. "Take them down and show them what the Arlong pirates can do!" The fishmen began attacking with Bakugou using his explosions to keep them at bay. "Hatchan! Stop the kid!" "But-" "DO IT!" The octopus fishman didn't like the idea, but went right in to send Bakugou down into the lower parts of the ship. "SON OF A BITCH!" "Please! Just leave and nobody has to get hurt that doesn't deserve to!" Hatchan looked at the ash blond in desperation. From the argument before, Bakugou began to piece together what was happening. "You're being forced to, aren't you?" Hatchan held his blades up preparing for a fight. "Maybe, but I can't let my friends down. They're counting on me to free them and in order to do that, Arlong and everyone need to escape alive." Bakugou came at the fishman with his blades ready to intercept.

Bacon top of the deck

Ochako, Momo, and Itsuka began preparing to face the fishmen with each one trying to take down as many as possible. Sadly, they hit a snag when Kuroobi came to attack Itsuka with fishman karate. This separated her from the group to face the stingray fishman alone. "So you can fight. But can you actually beat someone worth a fight?" Itsuka held her naginata out in front of her, pointed at the fishman. "Try me." Kuroobi came at her with Itsuka swinging upwards in hopes to make pull back. This didn't work however with Kuroobi moving to the side and giving her a solid punch to the side. The orange haired woman slid back before recovering to dodge a kick that destroyed part of the ship to come right at Kuroobi with a forward thrust. The fishman took advantage of his turning momentum to grab the naginata and use his hair to whip Itsuka across the face to cut her cheek. "So what are you going to do without this?" Kuroobi tossed the weapon behind him forcing Itsuka to fight hand to hand.

Meanwhile, Ochako had been separated as well by Chuu who she was trying to keep from hitting her with high pressure water shots. 'If one of those hits me, I'm done for.' "You won't escape me so easily." Chuu came back to punch her into the stomach to send Ochako back. "You might be strong for a human, but you're still nothing compared to a fishman *chuu*." The brunette grunted before getting up to continue her assault. She tried to fight as Hancock had instructed her, using her body's natural fluid motions as a woman to her advantage before getting towards Chuu to give him a solid kick to the side. This unfortunately did nothing besides giving the fishman something to grab as he reached for Ochako's leg and threw her across the ship and to the front. "Now what are you going to do, human?" As this went on, Momo had to struggle with several fishmen attacking her and the captives they were trying to save for nothing to be working. No matter how many times she attacked the enemies, she wasn't strong enough to harm them to take them down and keep them down.

Across the ship, Izuku wasn't having any better luck as Arlong was far faster and stronger than Izuku for him to struggle even landing a hit. "Is this the best you can do, human? You're pathetic!" Izuku panted as he got up realizing that now he had to go all out and use what he learned within the week with Zoro and the Strawhats.

https://youtu.be/SEDnNDNU0J0

"You know something Arlong, you were exactly what I needed." He pulled his sleeves up to reveal weights on his limbs before letting them go. Thanks to his hardcore training regimine, Izuku's total weight on average was over a ton on average. "Now time for the second part." Pulling Muramasa out, Izuku placed the cursed blade in his mouth as well as holding his two other blades up. "Three sword style. I've been waiting to find someone worthy to test my training with this on." Meanwhile, everyone on the ship was preparing to show what else they knew from their training. Bakugou found himself excited as he could show what he learned. "Guess I'm using what cigar man taught me." Hatchan came at Bakugou for him to shout and disappear. "Shave!" He reappeared behind Hatchan before putting his finger out. "Finger Pistol!" This stopped Hatchan, but it didn't for long. "Time to see what this Rokushiki shit can really do."

On Momo's side, she decided to clear her mind and listen to the voices around. "Right." She dodged and struck an attack on the right. "Two left." She did the same taking on two different fishmen on the left. "Three forward and one above." She used the one above as a shield before sending all four out of the direction. "I won't let you lay a finger on these four." Itsuka began calming her breathing with what looked like a strange vibration happening in her hands. "That won't do much against me!" Kuroobi came at Itsuka with his fist doing next to no damage for Itsuka to put her hand out and send the fishman across the ship. Looking at her, Kuroobi saw Itsuka take a fighting stance used in fishman karate. "Time to see what Jinbei's training can do." Along with them, Ochako started to smile. "Why are you smiling human? Are you giving up?" Ochako held her fist to the ground and her hand on her knee. "I have to thank Izuku and Bakugou when I get the chance. It's because of what they could do in the Sports Festival that made me wanna get stronger. Strong enough to become just as powerful as them and help when the time came. Now is that time." Her veins began to pulse upwards through her suit with the ones in her head and hands being shown. Eventually, her body became red and began steaming. On the inside however, her blood was pumping at an inhumanly high rate. "It's not perfect since I don't have the Gum Gum Fruit. But it's close enough to the original where my Mind Mind Fruit can do almost the same thing. Congratulations Chuu, you'll know what it feels like to have a fist with the blood pressure of someone doing twice the amount humanly possible could do. Let's go, Second Gear."

And that finishes this chapter. So I'll go into explanation about the powers and skills everyone gained somewhat later on during their fights. Hope you all enjoyed and thanks for reading.