Lee Jin Sung, currently known as Monday Kiz, is a South Korean singer, lyricist, vocal trainer, and composer. He graduated from Sanggye High School and later obtained a bachelor’s degree in Applied Music from Myongji Junior College and a bachelor’s degree in Postmodern Music from Kyung Hee University International Campus. He made his debut in 2005 as part of the duo Monday Kiz alongside Kim Min Soo with their first album "Bye, Bye, Bye". The pair released 2 more albums before suffering a tragedy when Kim died in a motorcycle accident in 2008 at age 23. Lee and the agency decided not to replace him and he retired from the industry for a few years. In 2010, he returned with two new members and the trio retained the same name and released three more studio albums and several EPs. In 2014, Lee was again left alone when the other members decided to leave the trio so he began his solo career and released his first album, "Reboot", in 2016 and decided to keep the group’s name. He continues to promote as Monday Kiz and has also sung several OSTs for dramas but does not appear much on TV.
(Source: Korean = Namu Wiki || Translation = MyDramaList)