Tomoya can pursue Sophie alone and the route is a textbook affair, they have several sex scenes where they downright engage behind Marie’s back, lying about what they are doing on closed doors, with Marie being duped till the end, not much hard feelings on Tomoya and Sophie’s part since they take their affair as a casual fling, Sophie isn’t trying to replace her daughter and Tomoya wants to be with Marie. On the other hand, by pursing the oyakodon path with Sophie and Marie everyone is happy and in agreement, no looming bad vibes of an affair since Sophie’s husband is not event mentioned beyond just recognizing he exists back in the United States and that isn’t doing his natural obligations, thus Sophie has been left hanging for a long time.