In 2001, Yesung's mother Im Bo-kyung signed him up to audition for SM Entertainment's Starlight Casting System, in which he impressed the judges with his "artistic voice", and signed as trainee under SM Entertainment that same year.
Tahun 2001, Ibu Yesung Im Bo Kyung mendaftarkannya audisi di “Starlight Casting System” SM Entertainment, dimana dia mengesankan juri dengan "suara artistikny"-nya, dan menandatangani kontrak dengan SM Entertainment pada tahun yang sama.