Knowledge

It was no secret that he wasn't as knowledgeable as Lucien when it came to mana and supernatural word, so he always did whatever he did to learn some information about them from Lucien.

This was also one of the reasons why he respects the man so much even though he was way older than him.

Besides, what is age before power and knowledge?

Even if Lucien asks him to clean and dust his house every single day in exchange to teach him about mana and the supernatural world, he would gladly accept it and may even quit being a doctor for such knowledge.