This manga is the antithesis of everything that's wrong with Hollywood and Epstein's island. Fumi is a White Knight, he is a role model in how to counter the delusions of a pubescent teenager, while still taking care of her and her loneliness. And he is doing his work excellently, nonetheless.
He got heavy psychical burn marks earlier in his life though. The motivation is strong why he wouldn't risk anything with Ayano - e. g., not even getting into her flat, when she's sick and obviously needs some help. This is way less than what good parents would do. Still, for her it's more than she ever had...
For Ayano, it's important to learn that she can't just do as she pleases if she doesn't want to risk their careers. But there's no way to prevent feelings from happening, even when they are forbidden. The ethically most sober solution would be for him to continue to take care of her while keeping it purely platonic until she is an adult (and maybe chooses a future with him with a clear mind). This is my guess BTW where we are heading in the last chapter, "four years later". Or maybe even two years later. Yes, girls can marry at age 16 in Japan, if the parents approve.
But what am I writing... Better do some virtue signalling, ignore teens and avoid the problems they face in order to not get into trouble or - god forbid - be called a pedo. Everything's well in 'murica, fuck yeah!