A Promise [Luffy x OC]

Prologue

~Episode 324~

Xena (POV)
I squat on the top of the main mast looking at the Straw Hat Pirates raise their booze in celebration. I can't wait to join them... Once we were out of the Marine's sight, I made my way to the lawn, admiring the Thousand Sunny's structure. I was so in tranced by it that I wan't focusing in my surroundings. I sense Zoro behind me in defense mode.
Zoro: Turn around.
I slowly turn around giving them my front view, but the cloak I'm using is blocking off my identity.
Xena:I don't mean any harm Straw Hat pirates.
Luffy: You...
Chopper: You...
Nami: You...
Robin: You...
Franky: You...
Xena: Oh? I see you remember me.

~Nami's flashback~
Once Chopper burst through the wall, I saw a figure moving swiftly as if it was teleporting. I couldn't make out a face, but it smiled at me then led Chopper out of the room. This gave me a chance to beat one of the CP9, Kalifa.

~Chopper's flashback~
Even though my memory is still fuzzy, I remember seeing this person before. It was leading me up the tower, to where Nami was. Then it led me to where Zoro and Sogeking were. It helped me save my nakama.

~Robin's flashback~
Before Luffy and the crew jumped into the waterfall, this cloaked person appeared out of no where. I thought she was one of the CP9 but all the members were next to me and Spandam. When they all jumped in the waterfall she followed.

~Franky's flashback~
When I started falling (to what I thought was my doom), that mysterious person appeared out of nowhere and telling me, 'You're not gonna die today Franky.'

~Luffy's flashback~
I was stuck in the wall. Come on change back! When I look back to Lucci, he was charging at me. Suddenly I hear a crack and find that the bones is his legs are broken. Then a person in a cloak appeared and disappeared in a blink. I wonder who it is?

Ussop: W-Who a-are you?
Xena: I would love to tell you, but Zoro is still in defence mode.
Zoro lowered his swords and I lowered my hands.
Xena: Portage .D Ace sent me.
Luffy: Ace sent you?
I nod to his question, and remove my cloak, revealing my ombre hazel eyes, tattooed arm, long raven hair with silver ends and outfit. They all stared at me, with widened eyes.
Xena: Uh....
Luffy, Sanji, Zoro, Ussop, Franky, Chopper: YOU'RE A GIRL!?!?!?
Nami: IT'S A GIRL!!!! YAY!
Thought the girls were happy, the boys still seemed shocked. I revert my attention to Luffy. He looks better in real life than in the poster. Also, him and Ace look quite alike.
Xena:Ussop!
Ussop:Y-Y-Yes?
Xena: Why don't you interrogate me and ask me questions so that you may know who I am?
Robin: That would be a wise choice.
A little while later, a table, a recorder and two chairs were set up. Ussop on one side and me on the other. The rest of the crew stood by to learn about me.

Ussop: Name?
Xena: Xena.
Ussop: Where you from?
Xena: Centaurea in South Blue.
Ussop: Do you have a bounty?
Xena: Yes.
Ussop: How much?
Xena: You wouldn't believe me if I told you.
Zoro: I bet it's like 55,000 beli.
Xena: My bounty exceeds yours and Luffy's, Zoro.
Luffy: Nani!? (What!?)
Xena: My bounty is 750,000,000 beli.
Their skin tuned pale and they all fainted on the deck. I reach into my jacket, and take out an old wanted poster, with my name, face and bounty number.
Xena: See for yourself.
I place it onto the table showing them evidence. Zoro was still jaw dropped, and Luffy had stars in his eyes. Others like Ussop, Franky, Nami and Chopper are terrified.
Ussop: What did you do to get that big of a bounty?
Xena: Well a part of it is because I was with the WhiteBeard pirates for a while with Ace.
Robin: And the other reason why?
A small escape my lips bringing them all dumbfounded and confused. I see Nami take a closer name at my name on the wanted poster. I smirk, while I look at the fear in her eyes.
Nami: D-Demon Xena!?!?
Nami showed my poster revealing the nickname the world government gave me.
Xena: Hmph. You're right. Demon Xena. That's what I go by, but only because that's who I'm sharing my body with.
Sanji: Who?
Xena: Who else?
They all looked at me with petrified faces.
Xena: A demon.