You ended up becoming a demon when you were still a child.

You never killed any humans, you felt no desire for human flesh.

You were walking through the woods, normally. It was night, and you had some flowers in your hand. You didn't feel that Tanjiro was behind you with a sword in his hand, planning to cut his throat. But as soon as he saw you turn your head back he stopped instantly. "Wha..." Tanjiro said looking at you and realizing that you were a child demon.