The demon kid must have felt immense pressure due to being in the king's castle and the king's presence, and thus allowed the Divide Cock to be taken away. Normally Lucilla never let it out of her sight. That still feels like a blatant weakness in the plot because her whole clan gave their lives to protect it and to allow her to escape from the vampire attack. Yet, even if she feels social pressure in the king's castle, is that social pressure really heavier than the lives of all the people she used to know? This feels like a plot hole, even if it turned out to be nothing but a red herring.
