Ernst has been trying to successfully negotiate in helping Erika acquire her legally reserved portion of her inheritance from her great-grandfather Bastian Rosen, who is now deceased. 
He was sent to Japan shortly after the release of Flight-type magic by Japan's FLT company. His goal was to figure out how they realized the impossible and to learn of the identity of Taurus Silver. The identity of Taurus Silver is a well kept secret, and the information surrounding this magic engineer is amazingly powerful and clever. This mission was given top priority from Rosen's management, however with the discovery of Saijou Leonhard, he was forced to change his priorities. 
Ernst sent the Wahrheit sisters after Saijou Leonhard in order to capture him, however, they were unsuccessful.