Long ago in the wizarding world there was a young orphan child named Tom Marvolo Riddle till one day a professor from Hogwarts came to the orphanage to see him about his mysterious powers and to come to attend his school, his name was Professor Dumbledore(Headmaster of Hogwarts). You see when young children turn 11, they get their acceptance letter to wizarding schools, and he was a kid with strange powers the other kids at the orphanage didn't like. So he decided to go to school and learn to use his magic, he was a wonderful student but as the years go by he started to be interested in dark magic with no one the wiser to notice. Not until after he graduated from school, which is usually after their 7th year of school, though they didn't know it was him… After he graduated there was a Dark wizard who was killing a lot of non-pure blood wizards, and his name was Lord Voldemort, you see he didn't want to die, so he created items that can carry his soul, they are called horcroxes. Then around a couple of years after he hears of a prophecy about a child who can destroy him, it Said -

"The one with the power to vanquish the Dark Lord approaches ...born to those who have thrice defiled him, born as the seventh month dies...and the Dark lord will mark him as an equal, but he will have the power the Dark Lord knows not …and either must die at the hand of the other for neither can live while the other survives...the one with the power to vanquish the dark lord will be born at the seventh month dies…".

So what Lord Voldemort did was find the parents of the child who have defiled him and kill the child before it grows up, so he finds out it is the Potters who did. He went to their house late at night on October 31,Halloween and went to kill the child, but the parents got in the way trying to protect their child. So the parents were killed instantly , and he was about to kill the child, but his curse was deflected by a force he knows not, it was the power of another child, for the power the Dark Lord knows not is that he had a twin sister and left a lightning bolt scar on both children.

During that night the professor Dumbledore came to retrieve the children who are Harry and Dahlia Potter and send them to their relatives house to their aunt and uncle's house (plus their own child of course if you know the original story though I am not putting their names since most people should know them, and it won't be important in this story, the Dursley's), over the years the aunt and uncle used Harry and Dahlia as a housekeeper to do the chores and cooking for them, and they had to share a small room that can only fit one bed, one closet and a desk. They didn't have many personal items since they had to share and their uncle and aunt didn't treat them fairly at all and would be punished a lot and be put in the cupboard for 24hr to a week.

So when the children were 6 years old, their Aunt, uncle and their 7-year-old child were on a cruse ship going to Paris for two weeks for their child birthday. On the fifth day of the cruise there was a Marine ship sailing towards their ship, the captain had fallen asleep because they've been on the sea for a whole year. The captain had noticed too late and hit the cruise ship really hard since they were not going at a steady pace. The cruise ship was hit terrible and started to sink, the passengers were trying to get to the safety boats but not everyone will be able to get on one since it's a cruise ship with a lot of guests and plus the crew members. So about most of the 2500 people on board only 1700 are able to make it, but the Dursley's were not among them since It's hard to get to a boat when everyone is in a panic to get to one as fast as possible.

During this event do you know where our main characters were, Harry and Dahlia were in this, well they were at home, the aunt and uncle wanted to take their child on a celebration trip, but not their niece and nephew, so they don't have to worry about them and plus didn't was to buy more for two more ticket as cruises are really pricey. So they were home alone for a while, then one day there was a police officer who came and took them to an orphanage since they had no other relatives.

A couple of years later Harry gets adopted by a couple Daisy and Mathew Johnson and then Dehlia was adopted 6 months later to a couple named Violet and George Johnson, Dahlia's. The Foster parents of both children found the children had strange powers as they grew up, then in Harry's and Dahia's 11th birthday they received a letter of acceptances for each child.

Dear Mr/Ms. [Surname],

We are pleased to inform you that you have been accepted at Hogwarts School of Witchcraft and Wizardry. Please find enclosed a list of all necessary books and equipment.

Term begins on 1 September. We await your owl by no later than 31 July.

Yours sincerely,

Minerva McGonagall

Deputy Headmistress

So both children are sent on their way to Hogwarts school, Harry and Dalia were both excited to go to a new strange place and learn new things with other children. As they were going to gather supplies in Daigon alley and get coins exchanged, they found out they had a whole vault full of coins for the children. So as both children have gathered their supplies and had packed, they made their way to the train station 9 ¾ train (going by the original story how to get on the platform). Harry finds a compartment for him alone and the next part is how the original movie goes where he meets Ron and Hermione, then along came a brown haired girl with long hair to the middle of her back came in and asked if she can sit with them too. Once she sat she saw a boy who looked like someone she knew, and she asked him for his name and he said Harry.

"You look really familiar to me, reminds me of my brother, what is your name?" the Girl said

"Oh, its Harry ?" Harry said

"Oh I'm Dahlia"the girl said

"Dahlia?" Harry said

"Yes" Dahlia said

"It's me, don't you remember? I'm Harry Potter your brother, I haven't seen you in about 5 years" Harry said

"Brother?" Dahlia said

"WHAT" Ron and Hermione said

"Harry Potter has a sister?" Hermione asked

"Yes" Harry said

You see the wizarding world knows about the boy who lived, but no one knew he had a twin sister. So they make their way, train to the school, and then they ride the boats to the castle. So when they get there they wait to be sorted into their houses of either Gryffindor, Hufflepuff, Ravenclaw, and Slytherin then as they were waiting a boy with blond hair is on a stair and said

"Look who has finally come to Hogwarts its Harry Potter"(The foster parents let both children keep the last name to keep something of their real parents)The rest of the class whispered to each other that the boy who lived has come to Hogwarts. So they are led to the grand hall and wait to be sorted and Professor Dumbledore is telling them welcome to Hogwarts and then the sorting begins…

Professor McGonagall said -

HARRY POTTER!

He walks to the stool and sits, then she puts the hat on his head and the hat and was having difficult to decided because he has a lot of interesting features about him that would be put in all the houses.

He said

GRYFFINDOR!

And he sat at his table with the others, then the next person was called

DAHLIA POTTER!

People gasp and whispered that there was another Potter child though people never know it still can be a common last name, but it's not in this case, there is another Potter child, and it's a twin. She gets up to the stool and sits down on the stool, they put the hat on her head it says

Sorting Hat says hmm very interesting another Potter child, you have the pure heart and is really brave, also smart too since you seem to like to read… let's see where to put you … I think you should be in

GRYFFINDOR!

She went to sit at the table with her house and everyone cheered at the table for getting both Potter children.

So as the children grow as witches and wizards they (as the movies from Sorcerer stone to order of the Phoenix, but with a sister in tow). Then when Dahlia turns 15 her foster parents tell her they are moving to Japan for their work, so she moves to Japan with her parents and goes to regular high school since she is a potter and intelligent, but once when she has time she goes to the wizarding world and buys books for studying on her own of which subject she wants to learn. She goes to high school, so she can go into hiding until the final battle arrives, and to blend in with the city so no one suspects she is a potter. Also, since there was a war going on in the wizarding world, she told her parents about it and changed her name to Mai Taniyama so the Death Eaters won't find her. By now, Lord Voldemort Doesn't know about a sister, and he won't till the final battle.

So one day when Mai was going out early to school and found the cherry blossoms in nice bloom she went past the abandoned building she had heard stories about that it was haunted, she decided to go look through the window and saw a camera inside, so she went inside to see what it was doing there since it was so pose to be abandoned. As she was going to touch it she heard some yell who was there, and then she accidentally knocked down a shelf and had yelled help, and it was a man named Lin Koujo who blocked the shelf from her that was going to fall on her, but he got injured instead. A young man came in and saw what was happening, and his name was Kazuya Shibuya, and saw that his assistant had been hurt and asked Mai where the nearest hospital was.