He is good friends with Layton as he is among the only people who Delmona has told about his hair loss. At Gressenheller University he is seen while Layton and his apprentice leave. He asks why he's here because Layton was on holiday. Later on in the game he is seen again. Layton and Luke meet him in the Future London inside of the Hotel Duke. Near the end of the game Delmona turned out to be Don Paolo in disguise, because he had to spy on Layton while he was hired by Dimitri. He loves his granddaughter so much he always gets her the best and brightest gifts. He also appears in Professor Layton and the Last Specterin the chapter "London's Hidden Secrets",when Emmy returns to gather the documents for Layton.
In Last Specter, Dean Delmona gives the puzzle "Tricky Tomes" to Emmy while she is investigating London. He later can give to the professor the puzzle "Window Design" if he visits him in London.
Dean Delmona gives one of the puzzles in Unwound Future to Professor Layton and Luke. While they go to Gressenheller University he gives the puzzle "1/1000".