It was a collection of short stories.
My favorite was the one with that guy on the train who notices that his zipper is undone, and is considering how to stealthily zip it until a young girl taking a nap beside him falls face first, mouth open, on his lap. Then he pops a boner into her mouth. It wasn't really hentai since it didn't show anything, but the idea was enough for me to fap to. Plus the follow up with the guy standing and the sitting girl where he gets squashed into her face, then proceeds to pop a boner in her snoring mouth.