Both Luca and Duke are the same person in the sense that Duke is literally Luca from the past. Leone helps to awaken Luca, so that there is only one real Duke. However, Rere does not know this initially, although I believe she does find out later on. Luca is the male lead, and while he is the complete opposite of the previous Duke, Luca is attempting to make amends for the past Duke's immaturity. Ultimately, everything will be resolved in a satisfactory way.
Oh my goodness gracious