This is so funny because it literally happened to me. A middle-aged mom in the bookstore walked into the manga section, picked up the first book she saw without looking at it, said “she likes this stuff, right?” and walked off. As she left I noticed the book was shrink-wrapped (in the U.S., that is only done to books that are A) special collector’s editions or B) pornographic) and then glanced to where she pulled it from and saw it was yaoi hentai (yaoi referring to stories of love between men and hentai meaning pornographic anime or manga). It took me a while to work up the courage to talk to the woman, but when I did she told me she was buying the book for her 12-year-old niece. I explained what I did here, and also pointed out that many manga have an age rating printed on the back (once again, at least in the U.S. I’m not as familiar with other international releases) and that this one was rated for adults only. I helped her look around for something more age-appropriate and we settled on the Ocarina of Time manga adaptation.