The third and fourth Korean Wave booms are emerging mainly among the younger generations in Japan, despite the ongoing conflict between Korea and Japan due to anti-Korea protest, export restrictions on major products, and the interruption of visa-free entry, which is increasing the difference in perception among generations. The purpose of this study was to investigate the main factors behind Bangtan Sonyeondan(BTS) representing the third Korean Wave boom at its center was supported by the younger generation and created a fandom and to identify the factors of the difference in perception of Korea between the older and younger generations in Japan. The rising popularity of BTS among the younger generations of Japan is based on the fact that the concept of Japanese idol (fans support inexperienced and immature idol to growth them) created in the 1980s has appeals no longer to the younger generation. They are enthusiastic about BTS, an idol perfect in all aspects and responding to and communicating with them always. It was shown that the most important reason for the difference in perspectives between the generations on Korea and the Korean Wave was that each generation trusts and watches different media.