A criminologist, and one of Tenma's former classmates; he helped Tenma by saving him from arrest and also acquiring information about Johan from all the criminals that Johan had met. He also helped Nina to recall her past, to the point of endangering his life. Rudy is able to get into some insight about Johan and how he works but despite all that he knows, he is still baffled by Johan's actions. Dr. Gillen is also a former student of Dr. Reichwein. First seen in Chapter 33.

(Source: Wikipedia)