Canadians banks sharing information

I am a Canadian living and working in Japan for over two years now.
My bank/brokerage firm in Canada is now asking me to change my account to a non-resident status, and in doing so is asking for my Japanese My Number.

My understanding is that I do not have to pay taxes on my foreign investment for the first 5 years of residency in Japan, and that since I do not have a PR in Japan, these are not taxable for ten years. Is this correct?

Also, will my Canadian bank automatically share my information with the Japanese government, or do I need to do this myself when I file my income taxes.

If I plan on staying longer than 10 years, should I stop investing in Canada, risking to see a huge chunk of my capital taxed in Japan?

Any advice welcomed.