This year there's a rumor circulating on Twitter, claiming that many young women are mixing their own blood into the chocolates, in the belief that this acts as a kind of love spell that will ensure their feelings are reciprocated.
The rumor gets even more stomach-turning, because there are also claims of mixing menstrual blood, saliva, fingernail clippings, and pubic hair into the chocolates. Japancrush.com has posted many examples of these Tweets.
Is there any truth to these rumors? That's hard to know. It's certainly possible people would do something like this. But one hopes that all the Tweeters claiming to have done this are just bluffing.
However, it's worth noting that the central premise of the rumor is correct. Blood has been used for centuries as an ingredient in love spells. It's part of Blood Magic. In addition, blood (as well as every body part imaginable) was used extensively as an ingredient in western medicine up until the Victorian period. The historian Richard Sugg recently published an interesting book about this widespread practice of medicinal cannibalism.
So it's plausible that some young women would act upon these ancient folk beliefs and add a little something extra to the chocolate.