The allure of Big Katsu, a popular Japanese delicacy, has been dramatically amplified as it becomes a vital part of "oshikatsu," a fan lifestyle centered around favorite celebrities or interests. The sudden surge in sales has left the company president in awe, who had not anticipated this interesting turn of events. This unexpected popularity rise is largely attributed to the digital fan culture in Japan.

In Japan, "oshikatsu" or fan activities, often entail various forms of merchandise or rituals that symbolize a connection with the fan's idol. The followers have adopted Big Katsu in their fan activities, leading to an unforeseen popularity surge for the delicacy. The trend showcases the influence of fan culture on consumption patterns in Japan.

This is similar to how trends are set and picked up in the US and the EU. Be it celebrity culture or a popular trend, growing fan bases have a strong impact on consumption, often leading to unexpected spikes in sales, just as Big Katsu has experienced in Japan.