Highlight's Yoseob revealed that he had been diagnosed with COVID-19 two weeks ago and explained his reason for hiding it.

On June 10 KST, Yoseob kicked off his two-day solo concert series 'BITTER SWEET,' held at Olympic Hall in Seoul's Olympic Park. 'BITTER SWEET' is his first solo concert in five years, following 2018's 'White' concert.

Toward the end of the concert, he confessed, "I think concerts are the time when I can be the most honest with you all. [...] I think there were a lot of really difficult moments while waiting for this moment to meet you all. After fighting off various colds that were not going away starting in May, I also got COVID-19 two weeks ago." He then added, "I'd been hiding it well because I didn't want to burden everyone [ahead of] this performance."

Meanwhile, Yoseob also admitted that he had adjusted the setlist for this reason, explaining, "I think there'll be songs you want to hear. Since I'm not in the best state, I made this setlist while thinking, 'Let me try my best doing what I want to do.'" Overall, the setlist included 20 songs, including his popular solo tracks "Caffeine," "BRAIN," "Where I Am Gone," and "Star."