@TrueGoddessReincarnation Generally manga in Japan can't be published if it shows the Japanese being aggressive invaders against other nations, precisely because the government is now lead by the ultranationalist wing of the LDP who want to whitewash Japan's pre-WW2 history. Before that mangaka just don't want to tackle the issues of wartime crimes of the IJA and especially Japan's activities in Korea. Remember, South Korea was a Japanese ally throughout the entirety of the Cold War, so nobody wanted to remind them of past atrocities. As a result you won't find manga actually focused on Japan's occupation of Korea. This is different in the case of China, which remained an enemy throughout. You will find many manga covering the Japanese invasions of China in the early 20th century.
That's why I asked about the era. Many manga set in the Momoyama era will include a segment on Toyotomi Hideyoshi's invasion of Korea (the Imjin War). Yokoyama Mitsuteru's biographical manga on Date Masamune, Toyotomi Hideyoshi, and Tokugawa Ieyasu all contain fairly long segments on the invasion of Korea, seen from the perspectives of the main characters. Yamada Yoshihiro's manga Hyouge Mono even has the main character actually joining the Korean invasion (albeit for totally self-serving reasons) and gives a surprisingly historically accurate account of the war.
As for samurai media being banned in SK, this is no longer true. Ultranationalist Japanese media and jidaigeki glorifying samurai are still subject to censorship, but since 1998 the actual postwar ban on Japanese media had been lifted for most forms of it. In fact, depictions of samurai are now common in Korean media itself, particularly in period dramas. Anime and manga and movies based on manga depicting samurai are openly shown in Korea, mostly because they tend to espouse Japan's pacifistic postwar views and are sympathetic towards Japan's former colonial victims. Rurouni Kenshin live action movies were box-office hits in SK despite their sensitive subject (the movies' undertones depict the rise of Japanese imperialism). While there is still tension (especially now), SK is more open to Japanese media today.