Doesn't it follow a points system + length of time?

You can't have dual citizenship with Japan.

As much as they are a great country, there is a level of xenophobia there still. Even in the major cities. To clarify, if you are not Japanese they will be courteous to you but you will still be classified as an other. Take this however you will, but I have a sibling who works there, has a wife (Japanese citizen) and two kids there, and it is definitely one of the aspects that sounds the most grating. Especially when it comes to the potential, but subtle, ostracization of the kids when they are going through school

Resident is not the same as citizen, which is what OP mentioned. Having "resident" status in a country generally gives you many perks of being a citizen without actually becoming one. Usually things like being able to open a bank account, working legally, getting a drivers license, etc. with the "liability" of possibly having to pay into the equivalent of social security (and other things, can't vote for example).

This does not change any citizenship status on either side.