The story begin in the world of One Piece. While the Straw Hat Crew was sailing aboard the Thousand Sunny, Nami stood looking through the binoculars at something very far away flying above the sea surface at high speed heading towards them.
So Nami shouted in a frightened voice: "Hurry up, hurry up!!"
The crew started coming toward her, standing beside her and looking in the same direction she was looking.
Then Nami said, pointing with her finger: "Look over there! Something strange is heading toward us!"
Something appeared from far away, flying fast over the sea heading toward the Straw Hat Crew's ship, and the sea waves exploded behind it from the great speed of its flight.
Sanji said: "he is flying at a crazy speed..."
Chopper asked fearfully: "What?! is it a human?!"
As for Usopp, he screamed in sheer terror: "Aaahh move the ship!! It's going to crash into us!"
But, when it got close to the ship and was about to crash into it, it suddenly stopped in the air. However, the sea waves that were behind it hit the ship, making it shake violently.
Franky: "What was that?!"
The person who was flying fast appeared, standing in the air in front of the Straw Hat Crew.
The strange person said in a calm tone: "Sorry about that.. I was flying fast because I'm in a hurry.."
Zoro held his sword and said: "Who are you?!"
The person replied while smiling: "Hello everyone.. I'm called Trunks.."
Trunks raised the wanted poster he was holding, which belonged to Luffy, and began staring at it while saying: "If this is the right ship.. then no doubt you are the one I'm looking for.. Monkey D. Luffy."
Zoro slightly drew his sword and smiled, saying: "So you're a bounty hunter.."
Trunks: "No, this paper is just to help me in the search.. I don't know anything about this universe because I came from another universe."
Chopper said in surprise: "Another universe! Does that mean you're an alien?!"
Trunks replied with a smile: "I think you could say that."
Sanji: "Is that why you can fly in the air like that..?"
Trunks: "No, even humans in Universe 7 can fly.. all you need is training."
Chopper asked excitedly: "And what else can aliens do?"
Luffy jumped too and said: "Can you shoot lasers?"
Trunks: "Lasers? Maybe something like that.."
Trunks raised his finger, pointed at the sea, and fired three ki blasts from his finger toward the sea, and the blasts exploded above the water as the crew watched in amazement.
Luffy, Chopper, and Usopp turned to Trunks and shouted excitedly: "Amaaaazing!!! You can shoot lasers from your fingers!"
Trunks: "That's extremely easy.. my comrades can teach you ki and flying if you go to them in Universe 7."
Luffy: "Really? Yay! Hey Jinbe, turn the ship.. let's head to Universe 7 right now!"
Trunks said with a smile: "It's impossible to reach Universe 7 with just a ship.."
Luffy: "Why? Is it a really far island?"
Nami: "Because it's not an island, you idiot.. it's.. it's.. I don't know how to explain it.."
Trunks: "Alright.. maybe I can take you to Universe 7 later after I finish my mission here.."
Nami: "Mission?"
Trunks: "Yeah. I'm here on a secret mission and I want Luffy-san to come with me.."
Luffy replied quickly: "I agree!"
Zoro: "Wait, Luffy.. we don't know anything about this person.."
Luffy: "Don't worry, Zoro. He doesn't seem like a bad guy.."
Trunks: "I'll explain everything on the way.. let's go."
And quickly, Trunks grabbed Luffy's hand and flew high into the sky.
Luffy said while waving to his crew: "Goodbye guys. I'll be back soon, and we'll go to Universe 7!"
Trunks flew away at high speed above the sea, carrying Luffy with him.
Luffy said excitedly as they flew: "We're flying really fast.. this is awesome"
Trunks started explaining the current situation: "Luffy-san, listen carefully.. I'll tell you why we came to this universe. To be more accurate, we were sent here, to eliminate two people who came from our universe into this one. We don't know much about them but we found out where and when they will appear. But we don't know anything about this universe. That's why we asked for help from someone we met by chance as soon as we arrived. He agreed to help and take us to the time and place we want, but he asked us to bring you with us.. Luffy-san.."
Luffy turned while picking his nose and said: "Huh..? Did you say something?"
Trunks: "You didn't hear anything I said?! Damn. You're just like Goku-san.. anyway. Our comrades are waiting for us there now.. I'll increase the speed.."
Trunks flew while holding Luffy quickly until they reached Marineford, and Trunks and Luffy stood above the Gate of Justice.
Luffy: "Why did we come here?"
Trunks replied: "Our comrades are waiting for us in this place above this gate. Because the place where the two people we came to eliminate will appear is this place.. Marineford Island.."
But Luffy said in surprise: "Waiting for us? But we're already here. And there's no one here"
Trunks took out a capsule from his pocket and said: "Yes we arrived at the right place but not at the right time.."
Trunks threw the capsule and a time machine came out of it.
Luffy said excitedly: "Amazing! What is that thing?!"
Trunks: "This is a time machine. We'll use it to go to the time when our comrades are waiting for us in this place.."
Trunks jumped into the time machine and began operating it. Then Luffy jumped in after him.
Luffy: "What's this? It's so small and has so many buttons."
Trunks, while pressing buttons, said: "All I have to do now is some calculations to get the time exactly right. So we arrive at the time of the execution of.. Portgas D. Ace.."
Trunks' words shocked Luffy.
Luffy turned and said in a soft voice: "Execution.. of who?"
Trunks: "A person called Portgas D. Ace.."