This adaptation is just making shit up as it goes. The princess doesn't have this anti mana ability, none of this HAPPENS.
She was trying to solve the circuit and Raniel helped her out easily. It was a casual exchange in the novel. The way to solve the circuit was also explained in a neat way, to show that Raniel is truly on another level compared to the rest.
To kill the fish in the pond, everyone is trying to remove everything inside it. Raniel suggests poisoning the pond instead. (I might be messing up the details, but I'm not making shit up like this adaptation.)