Perfect Plan?

As he could not deal with him, how about letting Belle's father deal with him instead?

If he managed to persuade them to stay and continue the Quest, an 'accident' might happen, and at that time, all he needed to do was to put all the blame on Leon. He knew that Belle's father would believe him as he already gained his trust long ago. That was also the reason why he allowed him to become her bodyguard. 

He smiled inwardly as he thought that his plan was already perfect.

Belle knitted her eyebrows as he did not like Delo deciding anything for her. However, just as she was about to berate him for it, she suddenly heard Leon's calm voice beside her. 

"Alright then… but, you must remember, it's your duty to protect her, not mine. Earlier was just an exemption."