I guess idol cards can be filed under "those crazy things Japanese people do!", but America's done it too. Tobacco companies had series of beautiful ladies inserted in their products well over 100 years ago, and there are plenty of card sets issued in the 1980s through 2000s by Playboy, Hustler, and other adult magazine companies. And then there are all those Benchwarmer sets.
Japan has issued cards for idol singers for decades, generally in the form of bromides. Starting in the 1990s, standard trading cards for race queens and bikini models hit the shelves, quickly evolving into what we have today.
Just like Benchwarmer sets, Japanese idol cards have autographs, kiss cards, and relics. There are often Polaroid photos, called chekis, too.
Of course, relic cards for models are generally going to be clothes. So, buying relic cards, I guess I'm picking up some women's clothing. Anyway... Yuko Ogura is my favorite idol, and I found a cheap lot of relics from early in her career.
All four make for nice additions to my Yuko collection!