As you may know kanji, chinese characters, are used in China, Taiwan, Korea and Japan.
But did you know they are not all the same.
Each country simplified kanji in their own way, though most of them are similar enough.
In1991, scholars representing each country got together and agreed to unify the character style to avoid the confusion caused by the difference. The 8th conference was hold last year and the effort is moving forward though slowly.
Sharing character style might reduce the confusion but do not eliminate them completely.
"愛人(愛 means love. 人 means person.)" in Japanese mean "extramarital partner", "girl friend/boyfriend" in Korean, and "marital partners" in Chinese.