On the drive home, from the back seat, I was literally hit on, asked explicit details about private love-related stuff as well as about my manhood, had my hair and ears fondled. I thought I was going to pass out from all the blood racing from my head to my nether regions. I have never seen anything like it before nor since. Which is very, very sad!

When girls are in a situation in which they have the power or feelings of empowerment, they often shed the "polite" public veneer of "innocence" that they are expected to carry for sake of image to the adult aristocracy that controls them. Such was the case in the situation you told about here, where there was four of them and one of you, where it was very clear to them that the guy they were driving with was sane and not dangerous in any way & whom they felt comfortable with, and where they were coming off a "high" from the high octane concert environment that made them feel very "sexed up" in an empowered fashion. Suddenly, they were no longer pretending that they only thought of Barbie dolls and when they would have their next Pokemon game, but were actively thinking about dicks, sex, and the envy of their friend's older sister who had legal access to the guy in their midst.

What would have driven me crazy if I were in your situation would have been the realization that I had to be an "adult" and could not be part of those girls' circle as a peer, and worse, that society expected a guy with my sensibilities to instead get that fulfillment from a middle-aged woman that I am not in the least attracted to.