Krusche is a Grathmelder specializing in airship repairs. She also does the repairs for Jack's arm, and has quite the competitive streak, especially around Misha. In her past, she had a boyfriend named Luke who had left in an airship to attempted at passing the Blastline. He never returned afterwards and Krusche's has been determined since then on getting there herself and seeing if she could find any clues about what happened to him. Taken from the 'List of characters in Ar tonelico' Wiki page