you are the biological sibling of Rui Ayaki your little brother

Before when you and your brother were humans your little brother was born with a weak body and was very sick

He couldn't get cured, one day on a fine winter day he saw children playing in the snow he wanted to join them... As soon as he took a step out he could hardly take anymore steps and fell

Your mother rushed to him he was emotionless as he laid on the ground... Just when when would he be cured...?

One day a "Doctor" came to your place and said he could cure Rui, he gave your little brother a medicine but... He ended up becoming a demon

He was now strong and not sick anymore but he couldn't go out in the sun anymore plus he started desiring human flesh and blood

He devoured both of your parents when he was sleeping at night with you... He... Devoured your parents... He then turned to you noticed you still fast asleep and turned you into a demon like... Him...

Both of you started making a fake family but both of you were biological so you both weren't fake siblings you had a fake mother and father, cousins and some other more fake siblings

You all stayed at Mount Natagumo as a fake family you all were a fake family... It was a forced doll house where nobody could escape

All the members of the "Family" were forced not to leave the great play, you and your little brother gave power to them to protect themselves from demon slayers and play as a "family" member

It was night a dark night you all were doing your things then Rui, your little brother, came up to you interrupting whatever your doing

"Nee-san... Demon slayers have come to this land and have killed "mother"..." He said softly loud enough for you to hear emotionless