Double S 301 – Sorry I'm busybr After debuting with SS501 in 2005, Heo Young Saeng, Kim Kyu Jong and Kim Hyung Jun returned as Double S 301 with the mini-album "ETERNAL 5."br "Sorry I'm busy" is an urban R&B song with a modern beat and groovy melody. br It describes a busy man, who feels extremely apologetic to his lover.