Here's a few of my suggestions from the more recently published books. There are loads more keep in mind, remember to read the book notes!

Assimilating Seoul: Japanese Rule and the Politics of Public Space in Colonial Korea, 1910–1945 by Todd A. Henry, a professor of history at UC San Diego

Japanese Assimilation Policies in Colonial Korea, 1910-1945 by Mark E. Caprio, professor in the Department of Intercultural Communications, Rikkyo University in Tokyo

Park Chung Hee and Modern Korea: The Roots of Militarism, 1866–1945 by Carter Eckert, a professor of history at Harvard University. This one is more for if you are interested in the biography of one of the defining figures of modern Korea and how the colonial period leaks into the modern Korea.

Relating to that, there should be more books on history of technology and science in the colonial period. Japanese railways, mining, hydroelectric power, fertilizer, biomedicine etc. are all things that leak into the development of modern Korea. Especially the history of medicine is very interesting; Japanese colonial authorities use sanitation and biomedicine and the perception of "Korean dirtiness" to justify the colonization. It's a very interesting and lively area in Korean studies at the moment; it's unfortunate I can't think of any books at the moments, but there should be some you can search up.