Actually what turns someone on differs from person to person, and how sexually active they are/have been. A girl can cum just from having her breasts played with although this is more common in virgins than the “experienced housewife” that this anime is portraying. I would say it would make sense if she was as sexually frustrated as the anime was implying but this hentai has shown the girl masturbating so that doesn’t seem to be the case. In the end though it doesn’t matter since it’s still a fantasy world in which unrealistic things occur in, and can’t be seen in the real world which is why this type of porn is so appealing to some individuals.