Park Yu-ha, the professor who wrote “Comfort Women of the Empire,” in Seoul, South Korea.Credit...Jean Chung for The New York Times SEOUL, South Korea — WHEN she published her book about Korean “comfort women” in 2013, Park Yu-ha wrote that she felt “a bit fearful” of how it might be received. After all, she said, it challenged “the common knowledge” about the wartime sex slaves. But even she was