GOSHU IN (御朱印)
GOSHU IN is so to say a proof of pray (in a decent manner) at each shrine and temple. To be strict, it looks like a stamp book, however not.
Each stamps are hand written by monks as a proof of visit and pray. Those letters and stamps on the each page stands for the principal object (some temple/shrine has multiple principal objects and what to be printed is upon your chose). Thus, by carrying the book you can have the principal object with you just like wearing Rosary.
But amongst many young girls in Japan, GOSHU IN become quite popular and more casual one. Some says it is not a good trend (such as making light of worship), however, I "personally" think it is better than young people are loosing interests for Buddhism or any kind of religion.
I had also started visiting many temples and ask for the GOSHU IN. However, I am trying to leave my hand written copy of O-KYO. (a kind of holy book in Buddhism) just as my personal commitments..