TVXQ (also known as Tohoshinki for Japanese-language releases) is a South Korean pop duo consisting of U-Know Yunho and Max Changmin. The group was formed by S.M. Entertainment in 2003 and began as a five-member boy band. However, despite their commercial success, the group plunged into legal turmoil and internal conflict when members Jaejoong, Yoochun, and Junsu attempted to split from their Korean agency S.M. Entertainment. Forming the now JYJ

The group has broken major records and sales milestones and have been at the forefront of the Kpop wave especially in Japan in the 2000s and ongoing. Their Japanese single “Break Out!” released in 2010 was the fastest-selling single by a foreign act in Japan, breaking a record previously held by Elton John.

In 2008, TVXQ’s fandom, Cassiopeia was listed in the Guinness Book of Records as “the world’s largest fan club” with more than 800,000 official members.