I agree with Knight6797.
There is a really intimate feeling in this game and about this game. The artstyle first, of course, candid, but passionate and eager to convey what's going to happen to the girls. How Millie screams in shock, how the nun blushes, and this seducing look on their faces... of all the games I've played, I've always felt like the expressions of the girls in Boy Hero Ken were, not the most "realistic", but the most humane.
The setting too : Boy Hero Ken first takes place in some kind of gated community, where there are maximum 15-20 people in the village. The corruption has already happened as Hentai_Desu-ka? said, but it's not all the way done yet. It happens in an even more closed space : the manor. There's this feeling of "Grandpa could be molesting the girls right next to Ken that he wouldn't even notice" that feels omnipresent, whom IS omnipresent, and yet, Ken just doesn't get it, it's a thought that do not even cross his mind once, despite the years of abuse that Millie took in front of him. The top scenes for me were the kissing ones in the closets and the groping right after the bath.
I feel stupid to be happed by such a game, but I've yet to find one that feels as erotic as Boy Hero Ken.