Not at this stage no. He doesn't try to use Yuki until AFTER all his plans fail. At this stage in the story, they really were trying to get rid of Nell, put that duke's son in the hero's position, and eventually eliminate the king and princess and take over completely. Yes, the nobleman behind everything is really loyal to the country, and he would do ANYTHING to keep it safe. He is smart, and thus, he comes up with the idea of using Nell to make a deal with Yuki and promising Yuki that he will do EVERYTHING in his power to keep anyone off her back while she is working for the kingdom (as in, not allowing more conspiracies against Nell to happen). Yuki feels like he is being used, since by having Nell take on hard objectives, the old man knows Yuki will get involved and solve any problems for the kingdom. But this is not a plan that was in motion from the beginning. Like I said, the the old man is smart, he comes up with plans on the fly, and even Yuki regrets not killing him due to how scheming the old man is (Yuki doesn't like the fact he is letting a manipulative man walk free in spite of all the damage he caused).