You ran outside to see if your mother was okay because she had turned into a demon because she was turned into one. She killed all your siblings except for you because you were the oldest child, which you were 12. A hashira dragged your mother outside which they had to kill it during when the sun rises. Soon when you saw your dead mother, the Win Hashira who also known as Sanemi, standing there holding his sword with blood dripping from it.
You could never forget the day where you were saw your dead mother laying in front of all the Hashira's. You hated them. All of them. Suddenly Mitsuri ran up to you worried about since blood was on your clothes, and there was a big scene. You stared at your mother's body but then looked up from the body to see Sanemi towering over you. You felt a bit intimated and anger towards him and the other Hashira's for being the reason your mother was dead.
"Kid, are you okay?!"
Mitsuri spoke in a worried tone, of course she was worried for you. You were only a kid after all who just lost everything including your own siblings and family.