Fire Fist - One Piece X MHA Crossover

Prologue

As the pirates near freedom, Jinbe tells Ace and Luffy to stay in front as the Marines will want to target them. After the pirates steal a Navy ship, Akainu knows escape is futile and fires a lava fist at some pirates. Jinbe tells his two allies not to look back. Sakazuki gloats that the pirates would be cowards after saving Ace. Kingdew senses that Sakazuki is trying to send the pirates over the edge.

The Marine admiral then insults Whitebeard as a "washed up failure", driving Ace off the deep end. Ace turns to face Akainu in a fit of rage ignoring the pleas of his friends. Sakazuki tells of how Ace's biological father, Gol D. Roger conquered the Grand Line and started the Great Pirate Era by sacrificing himself. He also says that Whitebeard is a failure thanks to his lack of ambition and thinks he is a coward.

As Whitebeard will soon be forgotten, Ace marches forward covered in fire while Akainu thinks the crew has been deluded. Angered, Ace says there is nothing fake about the Whitebeard pirates while Sakazuki wants the pirates dead as failures. Determined to protect his father's era, Ace shoots a fiery fist while Akainu shoots a magma fist; The latter's magma easily breaks through Ace knocking him back. Sakazuki gloats that even if Ace is made of fire, his own magma can burn several times the effect.

Luffy tries to intervene, but drops to his knees as well as the Vivre Card. Seeing how he has the opportunity to end the bloodlines of Gol D. Roger and Monkey D. Dragon, Akainu aims for Luffy who is trying to reach Ace's Vivre Card. Seconds later, Ace's beads fall to the ground as Ace has shielded Luffy from Sakazuki's fist. The pirates and Garp are shocked as the Vivre Card begins to burn up again.

With Ace's Vivre Card burning up, Luffy looks on in horror. Akainu releases his fist while Ace coughs blood. The pirates are horrified at what Akainu had done to Ace. Kizaru, Aokiji and Garp look on in shock. Whitebeard turns back and sees the horror of Ace mortally wounded. Driven over the edge, the pirates angrily charge at the Marine Admiral. Buggy also looks on helpless. With the Seastone handcuffs too strong to remove from Marco's wrist, they insist on getting Galdino's help.

The pirates fire wildly on Akainu with the people on Sabaody looking on in shock.

However, Akainu recovers walking through the fire with only one arm. The admiral restores his arm and sets his sights on Luffy and Ace preparing another magma fist. Luffy tries to plead for his brother's life and Whitebeard tries to save his crewmate, but Kizaru fires a light blast at the large white-bearded pirate's arm. The yellow-suited vice-admiral reminds Whitebeard that he's become forgetful at his age. Just as Akainu's fist is about to hit, Jinbe blocks the attack willing to sacrifice himself for Ace and Luffy.

Marco then sees that Galdino is unharmed and demands he unlock his cuffs.

Garp decides to walk through his own marines, but Sengoku holds him down. The former tells him to hold him down as he could kill Sakazuki at any moment. While Jinbe recovers his hands, Vista and Marco use Haki-infused attacks on the admiral. Akainu gloats that the marines already won as Ace is finally dying.

Luffy embraces his brother trying to put pressure on the wound, and hopes to get help. But Ace thanks Luffy for his effort but accepts his life has run its course. Luffy yells for medical assistance, and a doctor races to their side. The wounds are too great as Akainu burned through Ace's internal organs. Luffy calls to Ivankov but there is no hope.

Saddened, the young pirate mourns as he cried out weakly, "N-no way... You promised me! You said... That you'd never die.... No matter what! ACE!!!"

As the Marines fight more pirates, Luffy believes the fight is not over, and tries to tell Ace to remember his promises. Ace thinks about how he should never have been born and didn't deserve to live. Years ago, some people insulted the young Ace and thought of killing him. Ace stood up to them. A woman named Dadan scolded Ace for trying to hurt people.

"I wouldn't even have a will to live... If it wasn't for Sabo and a high-maintenance brother like you." Ace mumbled. "Oh yeah. If you see Dadan someday, say hello for me. When I face my own death, I even miss a woman like her."

"Like I said, don't say that you're gonna die!" Luffy interjected. "There is one thing that makes me wanna stay. That is my desire to see you fulfill your dream. But I'm sure that you can do it! Because you're my brother! That day... Like we promised that day, I have no regret... In my life."

"That's a lie! Don't tell a lie!"

"I'm not lying. Something tells me that what I truly wanted was not fame. Did I deserve to be born? What I wanted was the answer for that question."

Ace had lived without regret, and believed things could have been better had he deserved to live.

With his voice weakening, Ace speaks to Luffy, "I can't raise my voice to let everybody hear me anymore. Could you tell them... What I'm about to say now? Pops! Everbody! And you Luffy. Thank you... for loving someone like me who is good for nothing... And who has such bad blood in his veins... Up to today."

Ace bursts into tears that his friends loved him, "Thank you!" Ace smiles with tears in his eyes. His grip on Luffy loosening as he fell forward with life flashing through his eyes. The Vivre Card burns out completely and Ace dies with a smile. While Luffy lifted his head to the sky, crying his eyes out while wails and sobs escaped his lips.