You were cursed by a wizard before you were born it is his son familiar. Then when you were of age a wizard your age or older collected you and you lived with him doing errands and he turned you into a crow when you had to go off delivering letters for him, though it was rare he sent letters out.

In your crow form you caw at the window and it opens and you fly in hovering near Mana waiting for him to turn you back, which he does and you drop to the floor in your human form.