Posters in Tokyo’s enormous Shinjuku railway station are normally used for advertising commodities like cosmetics and food, as well as new films. But occasionally you may happen across a poster with a birthday message and a picture of a young man, often from a boy band and typically with impeccable looks.These posters are created by specialized advertising companies and are paid for by adoring fans. They are part of a phenomenon called oshikatsu, a term coined in recent years that is made from the Japanese words for “push”...