Kouga Yun began her career as a doujinshi artist by creating works based on popular manga and anime such as Saint Seiya, Captain Tsubasa, and Maouden. She later debuted in a commercial magazine with her original work Metal Heart, which was serialized in Comic VAL from November 1986. Afterwards, she continued to contribute to numerous doujinshi works. However, the disbanding of a doujin circle she founded led to several breaks from commercial projects and resulted in some incomplete works. During her time in middle school, Kouga Yun was an avid fan of Masami Kurumada's manga series Ring ni Kakero, Fuuma no Kojirou, Saint Seiya, and Bt X. After sending numerous letters to Kurumada expressing her interest, he finally agreed to meet with her at his workplace.
In an interview in the September 2006 issue of Puff, Kouga Yun revealed that she originally considered using the penname Kouga Jun but eventually changed it to Kouga Yun. Among her notable works are Loveless, which has been serialized in Monthly Comic Zero Sum since 2002 and is ongoing, as well as Tenshichou (天使庁). She has also worked as an illustrator for the literary magazine Faust. In 2007, Kouga Yun contributed character designs to the Sunrise anime series Mobile Suit Gundam 00.