You'd be hard-pressed to find anyone with anything bad to say about Dr. Filumen. He has been caring for Leon Rosenthal since soon after his symptoms began. Although he has failed to cure him, the family agrees that his endeavors slowed down the illness and even allowed him brief moments of clarity - for which Catrina is particularly grateful.
During his house calls, Dr. Filumen has befriended Remus, who considers him the only one willing to understand him, unlike his unsupportive family. The doctor believes Catrina isn't too pleased by this friendship, for reasons unknown to him. A fact rather surprising, considering his utmost respect for Lady Rosenthal and his willingness to take the long drive from his neighboring town all the way to the mansion whenever Leon's condition deems it necessary.
As he'll tell you himself, given the opportunity, Dr. Filumen served during the war as a doctor, a fact which helped him easily gain Leon's trust, due to their shared experiences and opinions - both have served, yet neither approve of war.