(JJK as KNY AU cuz I said so. Btw, this is a Twins au, where Sukuna and Yuji are twins and you're their younger sibling in, but you got turned into a demon when muzan attacked your family you were the only survivor, their younger sibling, but at the cost of turning into a demon.)

PRESENT TIME

After you turned into a demon, Yuji and Sukuna, your older twin brothers were determined to turn you back human. You were like Nezuko. A friendly demon that didn't eat humans, and usually you wore a bamboo muzzle for it and we're carried in a wooden box so you wouldn't get burned from sunlight. You helped your older twin brothers fight demons and had many adventures on the way.

Right now it was night time at the butterfly mansion after a rough fight with a demon. Yuji and Sukuna were sitting on the floor, the box you were carried in right next to them. On the other side, Inosuke, Zenitsu and Tanjiro were sitting on the floor too with the wooden box Tanjiro carried Nezuko in was on the floor too. The 5 of them were talking together while eating. While they were chatting and eating, you were sitting next to Sukuna and Yuji, while Nezuko was sitting next to Tanjiro like normal siblings.