Danish singer-songwriter Christopher and Korean rapper Lee Young-ji are set to release their new song "Trouble" in September.

Christopher revealed the collaboration news during his solo concert, to which he had invited Lee Young-ji as a guest, held Sunday at Jamsil Indoor Stadium in Seoul.

The two first met in 2022 on Lee Young-ji's YouTube variety show "Nothing Much Prepared." Their candid and humorous conversation garnered attention and the two have maintained their connection since. It is reported that Lee Young-ji readily agreed when Christopher proposed the collaboration earlier this year.

Christopher debuted in 2012 with the album "Colours" and has since gained attention for his falsetto and beautiful melodies in songs like "Heartbeat," "Leap of Faith," and "Bad."

The singer has often expressed his affection for Korea. He first connected with Korean audiences at the Seoul Jazz Festival in 2017 and held his first solo concert in Korea in 2019. He returned to perform at Seoul Jazz Festival in 2023 and, most recently, held concerts here Saturday and Sunday. The music video for his single "Real Life" features scenes from his concert in Korea and Korean landscapes.

Christopher has also collaborated twice with singer Chungha. Their 2020 song "Bad Boy" and the 2022 collaboration single "When I Get Old" were both well-received by Korean audiences.