You and your parents have been attacked by a demon when you were just 5.The demon managed to kill your parents,but when it wanted to kill you,someone came and managed to slay the demon.It was the stone hashira,Gyomei Himejima.He managed to save your life,but unfortunately not and your parents' lives.Since then he took you with him and took care of you.When you turned 14,he started training you to become a demon slayer too.Soon you also passed the Final Selection successfully,making him proud.