Chaos Theory

"It is near..."

Chiaki heard Rukia's mutterings as she made her way into the room, with Chiaki herself staying quiet, not wanting to interrupt this key moment. Chiaki could have intervened in this case but…. She knew that could definitely backfire on her in the long run. It was easy to try and use your knowledge of a series to make things better or give you a good life, but the more you meddled, the more you'd change, and the less you know, the more likely you are to end up getting yourself killed. That was always the biggest mistake made by those kids in the isekai novels after all, so she decided she would keep her knowledge of how things would go locked away, only for the most extreme situations.

"It's near my ass! Sis, wake up, we got a burglar to deal with!"

Chiaki proceeded to make a show of pretending to wake up, as the intruding shinigami fell over, startled by the fact that she was visible and also the foot that Ichigo proceeded to ram into her behind.

"You can see me?"

"Yeah, why wouldn't I-."

Just like the original story, Ichigo was interrupted by Isshin barging into the room, though in this case with a fast elbow to the gut.

"Chiaki, tell your brother to stop being such a delinquent and not make so much noise!"

"What the hell are you talking about, can't you see…"

"…Bro, he can't see ghosts, remember"

Ichigo, quickly regaining his composure from the blow, looked up towards Chiaki, taking a moment to process the entire situation before grasping that the situation was spiritual in nature.

"Alright alright. Dad, get out of here, let the spirit mediums handle this."

Groaning, Chiaki watched Ichigo proceed to push Isshin out of their room (their ad muttering objections quietly the entire time), chuckling all the while. Rukia looked smug as she pulled herself up from the ground.

"Evidently your sister is the smart one between the two of you. Very well then, since you clearly don't understand the details, I'll enlighten you. I am Rukia Kuchiki… a shinigami."

Chiaki suppressed a full on laugh as she saw Ichigo struggling to grasp it, a sour look on his face the entire time.

"Yeah, I'm leaving this one to you bro, I'm not dealing with any dead people stuff"

Pushing Ichigo to deal with this on his own like he did in the original story, Chiaki wanted to make sure him and Rukia shared powers as they did before. At the very least, her brother seems to fall for the bait, rolling his eyes before giving Rukia an annoyed look.

"Yeah right, there's no such thing as a Shinigami, there's too many ghosts running around for someone to be managing them. You expect me to believe that when all these ghosts are always causing trouble?!"

Chiaki watched the two bicker and did her best to hide a smile; even when she was part of the scenario, she couldn't help but feel happy to see the story unfold in her front of her. It would be any manga readers dream after all. Leaning over the edge to see better, she saw Rukia looking very annoyed with Icihgo's stubborn defiance. Finally throwing up her hands in defeat, Rukia made a upwards gesture with her hands:

"I refuse to suffer this any longer. Bakudo #1: Sai!"

Suddenly, Chiaki was startled by a sudden force which pinned her arms to her back, leaving her lying face first on her bed, with her brother in much the same situation as he fell on the floor. Crap. She'd forgotten that was a thing that happened.

"Hey, what the hell is that for, I didn't even say anything!"

Rukia gave a frown, looking up and Chiaki, before sighing, the look of guilt on her face fully breaking the facade of being a mysterious shinigami that she'd been doing her best to uphold so far.

"I apologize, but I need to make sure no one does anything rash while I hunt this Hollow…You may not be aware of them, but these are…. truly evil spirits, and they can't be compared to normal ghosts as you understand them. As a Shinigami, it's my job to make sure no humans get involved."

"That's bullshit!"

Chiaki and Ichigo both yelled in unison, but Rukia still only shook her head, clearly not willing to debate the issue.

"How you feel about it is irrelevant, the fact is-"

At that moment, a immense cacophony erupted from the floor beneath them, a mix of screams, crashing, and a demonic, ghostly laugh, startling all 3.

"The hollow's voice! I can't spare any more time with you two, if you want to save your family, don't make any noise!"

Rukia ran out with blinding speed, leaving Ichigo and Chiaki to struggle on the floor. Chiaki watched as, after a moment of struggling, a loud "SNAP!" echoed through the room, and Ichigo pulled himself to his feet and ran after the shinigami, leaving Chiaki to yell and continue struggling.

"Wait, I'm not out yet Ichigo!"

Chiaki gritted her teeth, trying to figure out how to escape. She didn't want to get involved, but she also didn't want to be a sitting duck if the hollow came after her. Evidently Ichigo had instinctively released his spiritual pressure to escape, but try as she might, she couldn't release the bindings. Growling in frustration, she wracked her brain for the way to release it, trying to remember how reiatsu release worked. It was difficult in the heat of the moment, but:

"Reiatsu comes from the beating of the heart, release the valve... Here goes nothing…"

Chiaki focused her mind on the beating of her heart, trying to sense how and when the blood pumped to gain conscious control over the power flowing through her, to coax it through her body, out of her hands, and into the invisible restraints. Teeth clenched, Chiaki struggled until, with a final burst of effort, her body surged with incredible spiritual pressure, obliterating the restraints with a resounding room. Now charged with her own well of spiritual power, Chiaki leapt down from her bed and looked to see where the hollow was, only to see Ichigo flying past her, already in shinigami garb.

"Get back sis!"

Chiaki's mind reeled from confusion; Ichigo wasn't supposed to struggle this much with this Hollow, and they weren't supposed to be fighting in the house at all. Then, everything clicked for her: she was in the house, and the hollow had probably focused on coming inside the house to her since she was an easier target than Ichigo, and eating her would fuel it's spiritual pressure to much higher levels. Ichigo had probably gotten focused on protecting his sisters and hadn't realized he couldn't swing his Zanpakuto well indoors until he was already inside. Chiaki realized that the two of them would almost certainly die here.

"No!"

The hollow's claws slammed into Ichigo's Zanpakuto guard and sent him flying into the wall. Without thinking, Chiaki legs began moving on their own, rushing forward with a speed that exceeded anything she'd ever reached in this life or the last, and fueled by her unleashed spiritual pressure, Chiaki rammed her body into the hollow, sending it flying through the railing and down the stairs. Surging with adrenaline, she rushed down to meet it, jumping down the stairs and ramming her foot into its skull with the full force of her weight.

"Just DIE!"

Taken aback by the strike, the hollow's head was driven into the ground, an audible crack which filled her with relief… up until she lost her footing and fell backwards from the recoil of the strike, falling backwards onto the stairs and dazing her. Before she even had a chance to curse though, the stunned hollow shook off its shock and was upon her, reaching out with blinding speed to grab hold of her with its giant hand. Chiaki struggled with all her might, but the rush of power she felt had dissipated when she hit the ground, and she couldn't focus her power through her daze. The hollow began squeezing her with its long bony fingers as it tried to drag her into its maw. At the last moment, Chiaki found a burst of strength and with a Herculean burst of reiatsu reinforced strength pried the hand open and pushed the beast away.

"Look out!"

It was then Ichigo came down from the floor above, and with a final strike from his massive blade, cleaved the hollow's mask and head in two. Everything was silent for a moment - and then the monster's body fell to the ground. Ichigo followed soon after, letting himself fall to the ground, reeling from exhaustion, as Chiaki laid on the stairs. Breathing heavily, Ichigo turned towards Chiaki and gave a smirk.

"Guess you can't ignore all those spirits huh?"

"…I guess not."

As the adrenaline wore off, Chiaki felt the toll the pain and exertion had taken overwhelmed her, and she drifted off into the deepest sleep that she'd had in a long time.