Books containing hate speech against Koreans and the Chinese have become a common sight in Japan’s bookshops. The publication of ‘hate books’ has increased in tandem with the struggles of the publishing industry and the deterioration of Japan’s relations with South Korea and China. This article seeks to explain the causes of Japan’s hate book phenomenon, with a particular focus on books targeting Koreans. While South Korean researchers have mainly identified rising nationalism in Japan as the key factor, Japanese analysts label peculiarities in the Japanese publishing industry as the main cause of hate books. We argue that both these explanations are necessary but ultimately insufficient because they ignore each other’s key findings. We propose a synthesized explanation that takes account of both the role of nationalism in creating demand and the unique structure of the Japanese publishing industry, which tends to incentivize the supply of hate books. The article also shows that nationalism only translates into hate book demand in times of diplomatic crisis.