(This one might be a bit rough) Kalrheinz or Reinhart, as his current disguise is named, is the school’s doctor. Though he could be doing something much more productive, he’s really only here to make sure his sons don’t screw up his plan. So naturally the best way to ensure that is to become the school’s doctor, which is why he created the alias Reinhart. After all it would be too suspicious if he came as Karlhienz or Tougo Sakamaki the politician. So he decided to go a more subtle route.