Valentine's Day:
In Japan, it is the custom for girls to give chocolates to boys. This is not necessarily only for romantic purposes (though of course this is the main idea); it can be out of courtesy, to friends or colleagues for example. "Courtesy chocolate" is known as giri chocolate.
Happy Valentine's Day!
White Day:
Conversely, on March 14, males are supposed to give reciprocating gifts to anybody who gave them a gift on Valentines Day. In theory, the gifts are supposed to be more expensive than what was received (two or three times more in fact)