Sending Japanese text from C# to JS (IE)

We would like our software to support Japanese and I’m having trouble with the text not going through the way I expect it to.
Basically the C# app has a webBrowser control that hosts a UI written in reactjs.
Messages (json object stringified) are passing from the C# code to the JS running in the browser. Reminder, this is IE since it’s a webBrowser control. We will replace it in the future, but that’s not for this discussion.
When I try to send messages with Japanese text, I can’t read it on the JS side and I fail to json.parse the data.
It does work if I change 3 values in the Japanese OS registry (ACP,MACCP,OEMCP) to 65001 (unicode\utf8), but I don’t want to make changes to the Japanese machine because my software is having issues.
What I tried is on the C# side:
byte shiftJisBytes = Encoding.GetEncoding(“Shift-JIS”).GetBytes(msg);
string base64Encoded = Convert.ToBase64String(shiftJisBytes);
m_Host.GetWebBrowser().Document.InvokeScript(“receiver”, new object { base64Encoded });

but however I try on decode it on the other side, the string are always broken.
For the answers please remember this is IE running the JS.

I am lost with this, I can’t figure out how to pass this data to the JS.

Help will be appreciated.