MC-kun should understand that no one likes a donkan. Greenhair tried to rape this guy's girl at least twice, and he continued hanging out with him long enough to hear him comment on his denseness and then tell him to stay that way.
Why, for some mysterious-and-unexplained-yet-benign reason?
No, it's because Greenhair wants to rape her, obviously--the only person saying it's almost time for her to go is the same person who tried to send her off in the first place. That milquetoast denseness is what enabled Greenhair to keep coming back, after all.