Yun was born in Incheon. His family is Catholic. He later moved to Seoul. While he was a student, he began writing and poetry. In March 2000, he started going to Incheon Seil high school. At high school, he came out as gay. This made him isolated from his classmates. By November 2002, he left high school. He began living in a neighbourhood of Dongdaemun District of Seoul.