Hisui said the first step to learning the Balaur language was to catch a Balaur alive, so you caught a Draconute with the help of Sinjah in the Krakon. Sinjah told you she'd bring the Draconute to the fortress, and she sent you to go to Grunn. Grunn sent the Balaur to Kaoranerk, a Shugo inventor who built a machine that teaches people the Balaur language very easily. Kaoranerk had you retrieve a Language Crystal from Phosphor in the Temple of Knowledge for his machine. You brought back the Language Crystal and took it to Kaoranerk. His machine taught you to understand the Balaur language. Hisui said she'd surely give important missions to you in the future.