Masquerade centers on the Hiraga bloodline, of which Gen is a member. Having recently been orphaned, he moves into his grandmother's home and inadvertently activates the Hiraga clan's curse, under which nearly every member lives a tragically short life. At his grandmother's house, Gen starts to piece together faintly remembered memories from a dream he has always had. Assisted by an American graduate student, they attempt to reveal the secret of the Hiraga lineage, the whispered legend of immortality encoded in his genes, and a method to prevent Gen from meeting the same fate that all his ancestors have endured.