you are Tanjiro and Nezuko's Sibling.

you always stick with them,being the younger one.

you are also a demon like Nezuko,and you have a mark the same as Tanjiro's.

after a fight with uppermoons with Tanjiro,Nezuko,Mitsuri,Muichiro.

You and Nezuko finally demonstrated the ability to speak and survive in sunlight.

you two have no problem,but Muzan is coming after you two.

thats why you two are protected in the Butterfly Mansion.

Tanjiro is in another room,while you are in the same room as Nezuko,you two are staring at the sun at the window.