It can't be called grooming if the woman involved has never had that intention and still doesn't. Also the person who raised him was the butler. She just stepped in after the butler did the hard work, attempting to be friendly so she doesn't get killed later. Not a mother figure, but a guardian. And he doesn't understand sex or love, he's just crushing on her like a pure child. So why is everyone upset? My guess is he'll leave later, either to escape his feelings or to prove himself a man, because she will reject him. After he returns is when the romance will start.