"St. Valentine’s and White day…?"
"Well… St. Valentine’s Day is an occasion where lovers express their feelings for each other by sending letters or presenting flowers and confectionery like candies and chocolates."
"Although there is also a practice where females would give chocolate to the person they like as declaration of their feelings, or just to thank them."
"And that’s where White Day would come in. On the 14th of the next month, the males who received chocolates are obligated to return the gesture to the females who gave them chocolates in thanks. Does that help?"