A Yulen believer is a t.A.T.u. fan who doesn't want to believe that the 2 female members of the group were not romantically involved with each other. Yulen comes from taking the first 3 letters of each singer's name:
YULia and LENa
Though both singers deny this relationship existited there are still many Yulen believers amoung fans around the world. You can find them filling up forums with 'fan-ifctions' that involve the girls being in some sort of loving relationship.
Non fan: "Tatu pretended to be lesbians for money"
t.A.T.u. fan: " Tatu were forced to portray lesbians by their producer Ivan"
Yulen believer: "No they are pretending to be straight and they still love each other!"