In the haunting music video, he played a psychopath who killed the women he loved so that he could keep them. In 2015, Leo composed the song "On a Cold Night" () for VIXX's fifth single album "Boys' Record". Originally written as a duet between him and Ken, a studio version was released with the rest of the members performing for that album. On August 7, 2015, Jellyfish Entertainment released a video trailer on VIXX's official website after a mysterious countdown with a silhouette of VIXX's last special album "Boys' Record". As time went by, members of VIXX disappeared until finally only Leo and Ravi were left behind, which caused fans to speculate that it meant another comeback for all six members. A video trailer of VIXX LR was then revealed. VIXX LR was confirmed by Jellyfish Entertainment to be VIXX's first official sub-unit composed of rapper Ravi and vocalist Leo. Their debut EP, "Beautiful Liar", was released on August 17, 2015. On the same day VIXX LR held their first showcase for "Beautiful Liar" at Yes24 Muv Hall in Seoul′s Mapo-gu. In 2016 Leo was cast in the musical "Mata Hari" in the lead role of Armand from March 25 to June 12 at the Blue Square in Seoul. It was confirmed that he would be shedding his stage name and using his birth name Jung Taek Woon for the role instead, unlike his previous musical role in "Full House" where he was credited as Leo. On September 20, 2016, Leo collaborated with actress and DJ Park So-hyun to celebrate SBS Power FM’s 20th Anniversary and released the song "That's All" () as part of SBS Power FM's 20th Anniversary song project. Leo was cast in the musical "Monte Cristo" in the supporting role of Albert from November 19, 2016 to February 12, 2017 at the Chungmu Arts Center Grand Theater. On October 16, 2017, it was announced that Leo had been cast in the musical "The Last Kiss" as Crown Prince Rudolf. On July 21, 2018, it was announced that Leo will be releasing his first solo EP titled "Canvas" on July 31, 2018. From August 31 to September 2, Leo had his first ever solo concert LEO 1st SOLO CONCERT [CANVAS] which was held at Blue Square Eye Market Hall  On May 14, 2019, Leo announced about his 2nd Solo Concert [MUSE] which will be on June.