I don't think there's any member of my family I would fuck, because that would litterally wreck my relationship with them, and also I don't have much sexual attirance to any of them.
But this is not about me and everyone is free to love everyone as long as it's mutually OK and no sexual minor is involved. (in my country the sexual majority is 15)
I really like that manga personnally. I like big gender gap mangas too, and incest mangas. As long as it's treated smartly.
There's a manga I really used to like, that was about a 35 yo writer and a 11 year old girl falling in love. It was very smart friend and very sweet.
We just have to keep in mind that when you are younger and in a submissive position (like student/teacher or child/parent), everything is really warped and creating a fair and positive relationship is super hard.