You were 9 months old when your mother had left you with your dad, Giyuu, to defend for yourselves. Giyuu didn't have anyone to take care of you when he was a swordmen so he took you with him to demon slayer HQ.

Where everyone loved you there and took care of you while your dad was in Missions as one day when you were in you're dad dormitory at his demons slayer manison, you were crawling with Giyuu komodo on and giggling. As Giyuu emotionless heart melted at the sight of this.