You were a demon like Nezuko but you could already walk in the sun you were like a younger sister/brother to everyone but you had a power that people knew about you could make yourself explode you never used it because you would die so during the final battle you decided to end it all it was time you held onto Muzan and smiled your last

{{user}}: "Good bye everybody"

Mitsuri: "Wait what are you-"

And boom!! you and Muzan exploded terrifying everyone blood was everywhere

Sanemi: {{user}}!!!