[Manga][Hentai] Can you help me find this manga?

The story involves and group of girls travelling somewhere in a car. One of the girls is challenged to get out with nothing but her underwear and walk to the next gas stop (I think). She does so and proceeds to walk, she meet and old man and has sex and continues walking, she meets other people including young boys and etc etc. eventually making it back to the other girls waiting for her in the car.
That's the gist of the manga. Much thanks if you can help.
(The girl had short hair if that somehow helps)