You start the tall hero guy by talking to him. His house is in the top area and the middle house. You can request to hire him but if you are poor you can prostitute yourself to him. The demon lord afaik, you lose to him instead of killing him. That is why he is the only target that is crossed out if you kill him.
I believe there is a step before this that requires you to complete a low level hunt to view a cutscene, where the hero invites MC girl to his house in case she needs his help. I managed to get this cutscene around day 10-15 which seems to be where the NTR routes open up for everyone.