Spouse Visa questions

I know this has probably been asked several times but I want to just double check with my circumstances if anyone knows answers to the following questions.

First I'll give a bit of background so you understand the gist of my relationship before hand. I'm currently a four year university student in the UK. 3 years ago I met my current girlfriend whilst she was studying abroad here in the UK. So we've been dating for 3 years, I've done a year abroad in Japan as well whilst I was with her and I've travelled there 6 times to see her and she's been here in the UK 4 other times to visit me.

So obviously I'm intending on marrying her so the first question I have. Would I be able to go to Japan and marry in Japan itself and then apply for a spousal visa whilst there at the same time? Might be a hard question to answer but thought I'd ask here first before enquiring further.

Second of all, is there a financial requirement for the spouse to have? I mean she works in Tokyo currently, full time at a job which earns here about 4,000,000 yen a year? I've looked for income requirement and haven't found anything so was just curios. Either way her parents are willing to cosign it if necessary.

I'm guessing if I get it granted you just renew it every 1-3 years depending how long the visa is issued for? How long does a spousal visa need to be before I could apply for some sort of permanent residency instead of having to renew it?

What are any of the possible problems you see me coming up against? Like I said I'm a student etc about to graduate, but I'm pretty sure the length of our relationship and how much we've met each other and studied at the same universities would be enough to prove it isn't just a sham?

Thanks in advance!

this question has been answered, regurgitated for soo many times. everyone say their is different but it is all the same.
FCS do a SEARCH, you know the one on top.

Anyhoot...

Marriage in Japan -
Double check with your GF at cityhall where you plan to get marry.
https://www.gov.uk/marriage-abroad/y/japan/opposite_sex
https://blog.gaijinpot.com/foreigners-guide-marriage-japan/

Once your marriage is recorded in Japanese system then you can proceed with the spouse visa application.
Note that there are two ways of going about the application,
1. Apply from outside Japan via COE route.
http://www.immi-moj.go.jp/english/tetuduki/kanri/shyorui/01.html
Read this..
https://www.japan-guide.com/forum/quereadisplay.html?1+159008

2. Change of Status, application within Japan.
If you come to Japan on Temporary Visitor visa and get married or with resident status and apply for change to Spouse visa.
http://www.immi-moj.go.jp/english/tetuduki/kanri/shyorui/02.html
Read this..
https://www.city-cost.com/blogs/Tomuu/MnyEw

Long story short, prep docs, get married, prep docs and apply for Spouse, hope for the best.
For PR, normally the route will be 1-1-3 or 1-3, best to applied when they grant you 3 year.