Random thoughts
So I was thinking about when they mentioned "Japan" again and I finally decided to check why they put Japan because though I don't know much Chinese but learned a bit, I only heard of one term for Japan in Chinese from my learning.
Then with a bit of research, I found out that in the drama, they used an ancient term for Japan but the translation put a modern translation and based on the information I got, it's like the translator(s) has to sacrifice when translating because if they translated 东瀛 (Ancient Chinese term for "Japan", not 日本 which is the more common term used now) as "The Eastern Seas/Ocean" which will probably confused non-native speakers or learners even more.
Yeah, just random thoughts since when I watched it and the term Japan came up, it felt kind of odd for me though I didn't understand why until I thought about the Chinese word again and decided to look up if 东瀛 (dongying) also means Japan then learned a bit more.