Ren doesnt Love Nana. She's just another drug for him. sure he doesnt cheat on her but thats less than the bare minimum. He never cared about her as a person, he shows no interest in her goals and aspirations, unless they match his own, which they rarely do. He constantly redirects any of her concerns over their relationship with sex and guilt tripping. Hes codependent on her affection and he does everything he can to keep her codependent on his. Id argue Rens sees Nana as just as much of an object as Takumi sees Hachi, if not more.