Ask questions about character sets in multiple languages. thank you!

I would like to ask about the multi-language character set problem. thanks for your requirements for Chinese and Japanese. I want to divide it into two relatively independent systems for running, and the Chinese data will be saved to the Chinese table in the database, japanese data is stored in the Japanese table in the database. The problem is: 1. during background management, the customer may use a Chinese operating system or a Japanese operating system. However, on the background page, you only need a Chinese page to ask questions about the character set in multiple languages. thank you!
I want to divide Chinese and Japanese into two relatively independent systems for running. Chinese data is saved to the Chinese table in the database, and Japanese data is saved to the Japanese table in the database. The problem is:
1. during background management, the customer may use a Chinese operating system or a Japanese operating system, but the background page only needs a Chinese page, insert values to Chinese and Japanese tables respectively. what should I use for the character set of the page at this time?
2. I use UTF-8 for the character sets of all tables in the database. now I use a Chinese operating system during the test. after connecting to the database, is it necessary to set names gb2312 before writing data to a Chinese table and set names Shift_JIS before writing data to a Japanese table?
3. the front-end is running on two independent systems: Chinese and Japanese. data is read from different database tables, how can we set the set names and page character sets after the database connection at this time?


It may be a bit difficult. thank you for taking a look. thank you very much.

------ Solution --------------------
Set names UTF8