The single, "Star Shell," is the band's first song since "Green Nocturne" released in December last year.
To promote the new single, the band will hold a concert, dubbed the "Nell's Season 201509," at the Woori Financial Art Hall in the Olympic Park in southern Seoul from Sept. 18 and Sept. 20, the agency, Woollim Entertainment, said.
Scores of the group's fans appear in the single's music video, according to media reports.