Jujitsu Kaisen x SukunaSibling!Child!reader

Introduction

Blood. That's all you're really used to seeing over 1000 years. Your "mother" was killed by a curse. You didn't really care. You were just using her to get what you want. The curse lingered, a black smoke hovered over your fake mother. You didn't really care to show a lot of emotion, but when you realized nothing was happening, you screamed to get attention and started the fake waterworks.

Principal Yagi got a call about a curse who killed a mother but left the child. He hung up the phone and headed out. It sounded like a killer curse. He arrives and notices the cursed energy and immediately neutralizes it. The cops watched him do his thing and nodded. The curse only shrunk around you. Once Yagi was inside, he noticed the black fog in the corner. He waved it away and found you. Your hair was a tad messy, your clothes torn, and red streaks painted your face. You saw the sorcerer and scowled in disgust in your mind. The hatred you have for sorcerers is big, but not big enough to kill them. They still need to spoil you. You act as if you're traumatized to get the pity of the big man, and it worked. He coos at you to get into his arms. You shake your head scaredly, "afraid" of what he might do. He pulls out a little plush from his pocket, smaller than his hand. It's one of his curses he makes, but it's not moving around to beat you up. You eyed the plush and hesitantly took it. Once you had it, Yagi carefully picked you up. He noticed your blank stare at the toy before you decided to put its arm in your mouth. Yagi gasped at your action, making you giggle slightly.
"I'm gonna take you somewhere, and it's gonna be scary looking, but I promise it's a good place." You stare at him with your big eyes. The plush still in your mouth. A cop comes up and offers a candy. It was a rainbow lollipop, and you looked at it in hunger. Both Yagi and the cop laughed at you before being handed the lollipop. You start eating it right away, and you nod in thanks.

Before taking off, Yagi adjusted your seatbelt in his car. You were holding the plush in one hand, with the loli in the other. He took one final look and deemed you safe to take to the school. He started to drive to the school when he heard your stomach rumble loudly. He laughed and took a turn to a store. He got out and unbuckled you before picking you up and taking you to a restaurant. You needed meat. Not just any meat,

Cursed meat. You needed to eat a curse. Since curse energy doesn't affect you, you need to eat curses to keep that resistance. The only curse energy that affects you is your brother's. Ryomen Sukuna.

Yagi had sat you down across from him with a kids menu. You look up, already knowing what you want.
"What do you want to eat, little one?'' He asked. You make a big gesture that you want meat. Steak would be a substitute. The whole cow would be better. A cursed cow would be the best. Yagi looks at you skeptically, unsure what would be the best course of action. He could ask for a big steak, and then give it to you. That'll work. He called a waiter over and ordered.
After getting the food, Yagi handed you the plate of steak. Your eyes flashed a red before resuming your human color. Yagi took notice that you weren't a normal kid. You grabbed the huge slab of meat, and before Yagi could scold you about manners, you'd taken a bite as if it were ice cream. The meat cut against your teeth so easily. It confirmed for Yagi that you weren't completely human. Yagi was frozen after he'd seen the meat be so easily bitten into, like you've eaten meat before. He takes into account your teeth and eyes, making a list of possible things you could be.

After eating, Yagi decided to try and summon the curse in the plush he gave you since it's a curse corpse.
He turned on the curse, but nothing happened. He tried to put more energy, nothing. You cancel out any cursed energy put out by a sorcerer unless there's a curse nearby.
He kept trying on his way back to the school, still no movement. He didn't know what was going on, and you laughed internally. Since Yagi made the plush, it wasn't already existing. The cursed energy wouldn't work.
After a few minutes, a giant traditional building came into view. You gasp at the majestic building through the window, this is a school?
Yagi pulled into the hidden parking lot and parked. He got out and picked you up from the carseat. He needed to see what you were, so he visited the clinic first. Shoko Ieiri was the school's doctor, knowledgeable in almost all curses and abnormal beings. With her medical and curse knowledge, she should be able to find out, right?
"I have no clue what they are. There's nothing in the books or records that you described other than the flash of the red eyes. But they don't emit cursed energy. They're not a curse or fully human. I'm sorry, principal Yagi." She said, looking down at her notes.
Yagi pinched his brow in frustration. He's gonna have to ask that blindfolded brat of his what you are. As much as Gojo is a pain in the ass, he gets answers even Yagi struggles to get.
He sighs and pulls out his phone. He mutters before a cheery voice echoes out of the phone. Shoko just raises her eyebrow as Yagi talks on the phone. You get a feeling to start crying randomly and wait to do so. About 5 minutes later, a white-haired male comes barreling in the doorway and starts to shout. Now, you cry. Yagi and shoko look at you as you start crying and blame who you learned was Gojo.