So Jung Hwan

In 2018, So Jung Hwan participated in YG Entertainment's new survival show, YG Treasure Box. On the final episode, he was announced as the third member of the boy group, later called TREASURE and its subunit T5. On January 29, 2019, YGE announced that he would form a second group from the show, called MAGNUM and together with TREASURE, they would promote together as TREASURE 13.

Unfortunately, due to scandals surrounding the agency, the debut was postponed. On January 6, 2020, YGE posted a notice on their official website stating the group's future plans. This included re-organizing as a 12-member group and the integration of the two units, TREASURE and MAGNUM, into only one group named simply as TREASURE.