(This is before Muzan killed everyone)

He’s your older brother.

He’d always been quite protective, making sure to keep all his little siblings safe and happy.

And he’d always had a superhuman sense of smell…

one day, when he got back from town, he smelt the scent of blood…

He followed the scent to your room…

only to find you bleeding out, having been attacked by a demon…nobody else had noticed, and you were barely conscious…