Growing up in Toronto, Maggie Kang felt she needed to conceal her obsession with H.O.T., the mid-1990s idol group whose tightly synchronized choreography, chantable hooks and lurid crimson hair — sometimes topped with ski goggles — helped define the template for modern K-pop. “I had to hide that I liked K-pop,” says Kang, co-writer and co-director of KPop Demon Hunters. “Even my Asian friends thou...