Fairy tail Natsu x OC x Gray Juvia's sister?!

Springs

~Lucy's pov~

After a long walk home I decided that we deserve to relax at the hot springs.
"Hey guys. I think I have just had the best idea in the world." I say
"What would that be?" Erza replies
"Hot springs" I sigh exhaustedly.
"You Lucy, are a genius" Erza states back.
Wendy and Kaori are happily talking and we all join in about hot springs and all the times we have been to them.
"I've never been to a hot spring, what are they like?" Kaori asks. I gasp in shock.
"Never?!" I scream. How has she never been to one?!!
"I've heard of them but I've never been bothered to go to one on my own" she says looking awkwardly at the ground.
"Girl, you have not lived!" I sing laughing.
"What do you do in them?" She asks.
"Well basically you go to a little, well kind of big bath house and you wear towels to go and lay in really hot water but the water is so relaxing it's like I big bath. You will love it!" I say happily holding her hands and explaining what they are like.
I look back and see Gray and Natsu holding there noses.
What's up with them?

~Gray's pov~
As we were walking back from Kaori's first mission Lucy starts taking about hot springs. I didn't pay much attention to it at first until Kaori started talking to Wendy.
"I've never been to one before, what are they like?" She says.
"Never?!" Lucy screams.
I start thinking about the hot springs.
"I've heard of them but I've never been bothered to go to one" Kaori says looking at the ground almost embarrassed.
"Girl, you have not lived!" Lucy laughs
"What do you do in them?" Kaori asks.
"Well basically you go to a little, well kind of big bath house, you wear towels and to into really hot water but the water is so relaxing it's like I big bath. You will love it!" Lucy says.
I instantly think of all the girls in there towels and my nose has an accident. I look at Natsu and see he had the same problem.
Lucy turns around and gives us both the most terrifying death glare I've ever seen.

"She's almost as scary as erza" Natsu whispers.
For the first time in his life the fire breather is right.
"No kidding" I reply trying not to be heard by the terrifying Lucy.
The terrifying Lucy huh? Never thought I would say those words in the same sentence.

~time skip~
"We are here!!" Lucy yells.
I jerk my head up and stop instantly crashing into something squishy. I look up hoping to see Kaori like in one of those romantic manga's but instead I look up happily and see one of the most depressing things... Ever.
"YUCK NATSU!! WHY'D YOU STOP IN FRONT OF ME!!" I yell aggressively.
"WELL SORRY MISTER POPSICLE, I DIDNT KNOW YOU WANTED TO GRAB MY BUTT!!!" He retorts.
I was about to yell the best comeback EVER when Erza kicks our legs out from under us. We both fall crashing down on top of each other.
"Say one more word and I swear on my life I will end you both. You're not ruining my hot spring trip" she says in a deep tone.
Yeah, I'll shut up now.

Feeling gross and assaulted by the perverted pyro, I stand up and start to walk into the bath house.

"Girls and boys both have to go into different change room so don't go with them" Lucy say, presumably to Kaori. Oh that poor innocent child.

~Lucy's pov~
Kaori seems fairly young.
"Hey Kaori, how old are you?" I ask. I'm 22 so she shouldn't be that much younger then me.
"I'm 19" she says.
SHES WHAT?!
"19?! YOU'RE SO YOUNG!!" I scream
"I'm only a few years younger than you Lucy!" She says smiling.
"Whatever, let's go put our towels on" I say and grab her hand.

~time skip~
Kaori and I walk out holding hands, I love the fact that I'm like an older sister to her.
I slowly sink into the relaxing water and sigh deeply.
I see Erza, Wendy and Carla walk out and sink into the water too.
A few moments of sighing and I open my eyes again.
"The water is so nice...." Kaori says calmly.
I look over too her and smiling.
"It truly is" erza replies.
"Kaori-chan, what's that?" Wendy asks pointing to Kaori's back.
"Huh?" Kaori says.
"Ohhh, you mean the scar?" She says asking Wendy.
"I think so, what is it from? If you don't mind me asking" Wendy says.
Kaori just smiles sadly. She turns so her back is facing us, ties her hair up in a bun and pulls her towel down lower so we can see her full back.
"Oh my god" I say with a hand over my mouth.
She has a giant slash shaped scar in her back. It takes up a little less than half her back, it goes from the top of her right shoulder all the way down to the bottom of her left ribcage.
"What happened?" Erza asks in a confused voice.
Poor thing.
Kaori pulls up her towel and undoes her hair, turns around and smiles at us.
"When I was little, after J-" she cuts herself off.

"My family left me, I was wandering around looking for somewhere to stay. I had nowhere to go so I went to the forest. Before I got to the forest however I was attacked by something. I didn't know what it was at first but it was really windy and it had a scythe. I looked at it and realised it was a person, his name was Erigor. I tried to run away but he hit me in the back. That's what the scar is." Kaori says and slides back into the water.

"We've met that fiend unfortunately" Erza says sighing.
"Yeah, he nearly took your arm" I say to Erza, awkwardly smiling at the memory.
"Are you okay?!" Kaori asks suddenly concerned.
"Yes, of coarse I am" Erza says laughing.
"He was scary" Wendy says
We all smile at her.

After almost an hour of relaxing in the water my fingers are all pruned up.

"I suppose we should be leaving soon" erza says.
We all step up out of the water and walk over to the dressing rooms.
I wonder if the guys are out yet?