Kim Hyun Joong, Heo Young Saeng, and Kim Kyu Jong, former members of SS501, have excited fans with the announcement of their upcoming reunion as the new unit FIVE O ONE. This reunion marks the celebration of the 20th debut anniversary of the iconic 2nd generation K-Pop group. The trio is set to embark on a special world tour starting in Seoul in July and visiting various countries globally. However, the news of Kim Hyun Joong's return to the spotlight in South Korea has sparked mixed reactions among Korean netizens due to his past controversies.

Back in 2014, Kim Hyun Joong faced charges and was found guilty of assaulting his ex-girlfriend, leading to a fine. Subsequently, further controversies arose when his ex-girlfriend claimed to have given birth to his son, confirmed by a DNA test. Legal battles ensued over custody and allegations of defamation and threats. In 2017, Kim Hyun Joong faced another controversy for driving under the influence. Despite these issues, he has been active mainly in overseas activities, including fan meetings and concerts.

The trio's comeback as FIVE O ONE has garnered criticism from some fans who feel that the essence of SS501 is incomplete without all five original members. Some comments reflect disappointment at the absence of certain members and skepticism towards Kim Hyun Joong's role in the reunion. There is a sentiment that the reunion is seen as a commercial endeavor rather than a genuine reunion for the fans.