Background Information
In this story Ichigo didn't need to use the Final Getsuga Tensho and has been married to Rukia for 15 years and they have had two children, twins, together.
17 years after the end of the war against Aizen a Garganta opened above Karakura town. The alarms in the Seireitei loudly blared as the reiatsu that emerged from it had a dense, evil, aura to it and was on a level not seen since the war against Aizen, with the sole exception being Ichigo himself. Just as quickly as they started though, they stopped, leaving the entire twelfth division fearing for their lives.
In the real world Rukia was making dinner for her family when she felt the reiatsu burst. She started to rush to the room that she and Ichigo share, but as she started, the reiatsu signature disappeared. She then went back to cooking. Twenty minutes later it was done and the Kurosaki family sat down to eat. When they were done with the washing and drying up they went to their lounge room and started to watch a movie, Bleach: Fade to Black. Just as it was starting they heard a knock on the door. Rukia felt a shinigami reiatsu coming from the person knocking on the door. Ichigo, not being able to differentiate between reiatsu types, opened the door expecting some door-to-door salesman, what he got though, was a tall, orange-haired, seventeen year old woman, with rather large breasts, jumping onto him, screaming "O-tousan," and giving him the biggest hug that he had received since Neliel had attempted to revive him in Hueco Mundo.
He fell backwards, the girl on top of him. Rukia started to walk over to Ichigo, a mark appearing on the side of her forehead. As she growled out, "Ichigo...," she rolled up her right sleeve, preparing to hit him. As the girl got up from Ichigo's prone form Rukia proceeded to hit Ichigo after asking "...what the hell does she mean 'O-tousan'?"
Ichigo got up, grumbling, and said, "how the hell should I know?"
The girl asked, "O-tousan, why is this slut hitting you?"
Rukia rounded on the girl angrily yelling, "What was that?"
"Didn't you hear me? Alright then, why is this..."
Rukia growled, but, before she could do anything, an arrow shot at the orange haired girl. The tall, black haired teen that shot it, asked, "what the hell are you doing?"
"What am I doing? I think that the real question is what're you doing?"
The black haired, fifteen year old, teen screamed "Me?" then, in a quieter, more dangerous tone, "You come into our house, jump on my father, and then you question me. I've heard enough, it's time for you to die."
"Eh?" the girl asked, before a spirit arrow was shot at her. She jumped up, making a platform for to stand on in the air, and looked down at the black haired teen, yelling "what the hell?"
"Kurosaki Hisana," the black haired teen announced before she tapped her right leg with a ring that she had received for her last birthday that allowed her to exit her body and take on a shinigami form.
"Huh?" the orange haired girl asked, confused as to why the black haired girl opposite her would tell her her name before they started to fight.
"What do you mean 'huh'? That's my name. I don't know the customs of your squad, but, in my family, we tell our opponent our name before the fight since, we figure, the person that loses would at least like to know the name of the person that defeated them."
"Huh, a weird custom if ever I've heard one, but alright, Kurosaki Masaki, at your service."
"What? Don't lie!" Hisana said.
"I would never lie about my name," Masaki said drawing her sword from behind her back.
Rukia, who was looking up at her daughter and the strange teenager, heard the conversation between the two, and thought "Masaki! No way, it's not possib..." then, as she looked on, she saw the orange haired teen, claiming to be Ichigo's daughter, draw her Zanpakutō. To her amazement she saw that it was almost identical to Ichigo's. Rukia then looked at her reiatsu more closely and saw that it bore a close resemblance to Ichigo's right after his Vizard training. Putting two and two together she figured that it must have been Masaki that came out of the Garganta earlier. She looked at Ichigo and asked, "have you got something to tell me?"
"No, nothing," he replied.
"Really, then look at Masaki's Zanpakutō, if that's not proof enough that she's your child, feel her reiatsu, remind you of anyone?" Ichigo fumbled with the collar of his shirt as he thought of any possible explanation. He thought back to the Winter War and came to a conclusion. Rukia came to the same conclusion as Ichigo did, at the same time and said "Neliel!" she then turned to Ichigo as she said the green haired Arrancar's name, only to see him look away. She demanded, "how many times did you sleep with that green haired whore?"
As she said that, a Cero came hurtling towards the house as Masaki had heard what Rukia had said about her mother Ichigo slipped into shinigami form and raised his hand, blocking the Cero. She announced, "if you dare say such a thing about O-kaasan again, I'll kill you."
Ichigo said, "That's enough," and brought the full force of his reiatsu to bear on both his daughters. "Masaki, I won't have you attacking any one of my family. Hisana, you should know better, besides, if she was serious, Masaki would be able to fight even on your uncle's level."
The two girls simultaneously said "but..." they then looked at each other, scowled, crossed their arms and looked away from each other. The two girls then slowly descended to the ground.
Ichigo said, "Alright, let's go inside now and talk this out." The two girls entered into the Kurosaki residence, followed by Rukia and Ichigo.
Momentarily the Kurosaki's gathered around the dinner table. "Alright, I now call this meeting to orde...urk!" Ichigo gasped as Rukia hit him over the head.
Masaki yelled, "Hey!"
A black haired fifteen year old, said "calm down, this happens whenever o-tousan starts to act like ojisan."
"Wait, what?"
"I'm Yukio, Kurosaki Yukio, Hisana's elder brother."
"By three minutes!" Hisana yelled.
As Masaki rubbed the inside of her ear, Ichigo said, "Alright alright, anyway, Masaki, why don't you start off."
"Alright...uhhh...what do you mean?"
"Introduce yourself, you know, full name, likes, dislikes, that kind of thing."
"Alright then, as you know, I'm Kurosaki Masaki, I'm seventeen years old, as tousan and...mmm..."
"Rukia," Rukia supplied.
"...right, Rukia, have probably figured out, my mother is one Neliel Tu Oderschvank, the former Third Espada. I was, apparently, named after your grandmother and raised in Hueco Mundo. I like ka-sans cooking and really dislike the frequency with which Grim-Otooji challenges me to fight him."
Ichigo scowled and spitefully said "Grimmjow!"
"Anything else?"
"Yeah, sure I've got one, why the hell haven't you contacted us before?" Hisana demanded.
"Well, my mother wasn't too sure if the Seireitei would take too kindly to her presence in the real world and decided that it would be safer if I could come here by myself."
"Okay."
"Just out of curiosity..."
"Yes?"
"Why did you attack me with a bow? I thought that shinigami only use a Zanpakutō." Ichigo's head fell to the table, its landing cushioned by his crossed arms. This caused Rukia and Hisana to share a bemused smile and Yukio to cover his eyes with his hand. Masaki looked between her extended family and asked, "Uh, what did I say?"
Hisana, still smiling, replied, "Well, you see, it's not really something you said. You see o-tousan, gets kind of annoyed when he sees me using the Quincy skills that Ishida-sensei taught me."
"Huh?"
"It's complicated."
"No it's not," Yukio stated. "Ishida-san is dad's rival. As a matter of fact, it's really identical to you and Amayah." Hisana crossed her arms and scowled at the comparison. Yukio said, "See what I mean?"
"Huh, kind of" Masaki replied.
"Anyway, before Hisana had even left her body the first time she saw aunt Yuzu using a spirit bow, also taught by Ishida-san, and thought it was cool and begged her to teach her. She did and Hisana was found to be somewhat of a genius with it, so aunt Yuzu asked Ishida-san to train her."
Ichigo said, "Enough about that!" not wanting any further discussion on the matter of his daughter's utilisation of Quincy skills. He then looked at Masaki and asked, "So, how good are you in a fight?"
Masaki thought 'oh no, o-tousan has the same look in his eye as Grim-Otooji.' Rukia looked at Ichigo with dread, knowing exactly where the conversation was going. Masaki said "I'm sorry, but can the whole 'let's fight' thing be put on hold for now?" Ichigo scowled and looked away.
Rukia sighed, seeing the same scowl that had somehow been passed on to both of his daughters, luckily skipping their son. She said "look, why don't we all go to bed and..."
Masaki then said, "Alright, I'm up for a fight now." Ichigo smiled in the same way that his eldest daughter now was, like there was nothing more that they would like to do other than cut the hell out of the other.
Ichigo, who still hadn't returned to his body yet, said, "I know just the place." He then walked round the table to where Masaki was and placed a hand on her shoulder. The two then disappeared from the room.
As the two left Rukia sighed and asked "so, I suppose you two want to go and see those two cut each other up, don't you?" Not really needing an answer Rukia sighed and said, "Alright, let's go." Yukio, being the only one still in his real body, exited it and, along with his mother, disappeared, using Shunpo. Hisana, on the other hand, used Hirenkyaku to achieve the same effect.