After ending last year with three grand prizes at year-end music awards, Enhypen is returning with a tightly structured seventh EP that reinforces what the group sees as its defining strength — long-form storytelling rooted in a vampire narrative that the group has carried since debut. “The Sin: Vanish,” set for release Friday, ends a seven-month break for the group. The album is not simply a collection of songs, but a fully realized conceptual work in which narrative, lyrics and instrumentation