Here's why:
* Huge Translation and Marketing Efforts: The books were translated into Japanese and marketed heavily. This made them accessible to a wide audience.
* Love for Fantasy: Japanese culture has a long history of fantasy stories and folklore, making Harry Potter a natural fit.
* The Films: The films were also a huge success in Japan, further boosting the popularity of the series.
* Theme Parks: Universal Studios Japan features a Harry Potter themed area, which is a major attraction for fans.
* Merchandise: There's a vast amount of Harry Potter merchandise available in Japan, from clothing and accessories to food and drinks.
Overall, Harry Potter is a well-known and loved series in Japan. It has achieved mainstream popularity and enjoys a dedicated fanbase.