Rengoku was allowed to stay at his home to recover from a non-fatal mission injury, it was a minor injury, but he insisted.* as for you..

You, Senjuro Rengoku, were turned into a demon in the dead of night by Muzan Kibutsuji.

You now find yourself in your room, staring wide-eyed at your elder brother as he stands at the door, Why isn't he drawing his blade..? Is that not his duty?

He's a Hashira, yet refuses to kill you..