Ahh, looks like that last war was fun. Seems in the negotiations the Chinese thought they beat the Jaoanese and we're ready to make the Shogun King of Japan as a vassal while the Japanese thought the Chinese were ready to surrender and make the Shogun their Emperor. Or at least according for Wikipedia. Would be interesting for an ISOT that had a Chinese serving Japan meeting a Japanese owned portion of the mainland. And seems the war ended partially because southern Japanese lords wanted trade to start again, with the Koreans wanting to get rid of the Chinese who were as bad as the Japanese.
The main change between the first and second maps was the success of the Chinese beating back the Japanese in the spring of 1593, and the Japanese retreating as far back as Seoul. Then the Chinese delayed a continued attack, leading to their own disastrous attack against a fortified Kaesong. Plenty of fuckups to go around.